PROGRAMME & ABSTRACTS
! General information! ! ! ! 4
! Programme!! ! ! ! ! 5
! List of Participants! ! ! ! 10
! Abstract of contributions! ! ! 14
Insights from Solar System planets! ! 14
Terrestrial planets! ! ! ! 22
Super-Earths and hot Neptunes! ! 31
Hot Jupiters: observations! ! ! 38
Hot Jupiters: models! ! ! ! 51
Young giant planets and brown dwarfs! 57
Davos is a winter resort in the East of Switzerland, at 1560 m one of the
highest town in the Alps. Its showpiece is the Conference Centre, which
hosts the World Economic Forum every year.
Previous Exoclimes conferences have taken place in Exeter, UK, in
September 2010, and Aspen, CO in January 2012. The objective of these
conferences is to bring together specialists of the Earth, Solar System
planets and exoplanets to discuss the new field of comparative
planetology outside the Solar System.
In case of need during the conference, contact the organisers at
firstname.lastname@example.org or call +41 77 418 58 12.
Emergency numbers in Switzerland are
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144 for ambulance.
Exploring the Diversity of Planetary Atmospheres
Davos 9-14 February 2014
8:00! Desk opens
8:50! Welcome address
Session: Earth-like atmospheres
9:00! Exotic atmospheres (review): Pierrehumbert
9:40! A new perspective on the inner edge of the habitable zone: Leconte
10:30! Paleo-climates (review): Abbot
11:10! Exoplanetary extreme space weather: Cohen
11:35! Terrestrial planet atmospheres in the aftermath of giant impacts: Lupu
12:00 ! Lunch break
17:00! Interior-atmosphere interactions (review): Elkins-Tanton
17:40! Earth’s interior dynamics (review): Tackley
18:20! Magneto-hydro-dynamics: T. Rogers
19:00! Evening break
Session: Exoplanet observations
8:30! Exoplanet transit observations (review): Desert
9:10! Characterising exoplanet atmospheres with HST/WFC3: Mandell
9:35! Revealing distant worlds with ground-based spectroscopy: Stevenson
10:30! Exoplanet eclipse/phase observations (review): Knutson
11:10! Observation highlights –
! Ground-based detection of water in hot Jupiters: Birkby
! Probing the atmosphere of non-transiting planets: Brogi
! 2D mapping of the eccentric planet HAT-P-2b: de Wit
! Mapping clouds in exoplanet atmospheres: Demory
! Measuring the reflection signal of HD 189733b: Evans
! Atmosphere of exo-Neptune HAT-P-11b: Fraine!
! Transmission spectroscopy of super-Earth GJ1214b: Kreidberg
! HST/STIS transmission spectral survey: Nikolov
12:00 ! Lunch break
14:00! Workshop on transit observations: Sing
Session: Clouds and hazes
17:00! Photochemistry (review): Moses
17:40! Overcoming remote sensing challenges for cloudy atmospheres: Barstow
18:20! Recent advances in exoplanet climate simulations: Showman
19:00! Evening break
Session: Circulation models
8:30! Exoplanet circulation models (review): Menou
9:10! Non-hydrostatic, deep-atmosphere hot Jupiter climate models : Mayne
9:35! Water loss from N2/CO2-atmosphere terrestrial planets: Wordsworth
Session: Evaporation and energy
10:30! Global energy budgets for terrestrial and gas giant exoplanets: Read
11:10! Models of exoplanet evaporation: Owen
11:35! Enshrouded close-in exoplanets : Haswell
12:00 ! Lunch break
Session: Outer Solar System
17:00! Titan’s atmosphere (review): Mitchell
17:40! Measurement of the atmospheres of Europa, Ganymede and Callisto: Wurz
18:20! Jupiter’s atmosphere (review): Kaspi
19:00! Evening break
Session: Brown dwarfs and directly-imaged planets
8:30! Brown dwarf observations (review): Apai
9:10! Results from the “Weather on other worlds” Spitzer campaign : Metchev
9:35! Doppler imaging of a nearby cloudy brown dwarf: Crossfield
10:30! Model brown dwarf spectra (review): Barman
11:10! Connecting low-gravity brown dwarfs and directly-imaged planets: Liu
11:35! The mid-infrared properties of directly-imaged planets: Skemer
12:00 ! Lunch break
Session: Synthetic spectra
17:00! Model exoplanet spectra (review): Fortney
17:40! Simulated transit spectra of Earth and Jupiter: Irwin
18:20! Poster session
19:00! Evening break
Session: Atmospheric retrieval
8:30! Chemical characterisation of super-Earths: Madhusudhan
8:55! A comparison of exoplanet retrieval techniques: Line
9:20! The atmospheres of GJ1214b and GJ436b: Benneke
9:40 ! Discussion
10:30! Helium-dominated atmosphere on Neptune-size GJ436b: R. Hu
10:55! Ionisation regimes structuring planetary atmospheres: Helling
11:20! Ocean transport in the climate of exoplanets around M-dwarf stars:
! Y. Hu
11:40 ! Atmospheric super-rotation: Lewis
12:00 ! Lunch break
Session: Earth-like exoplanets
17:00! Climate dynamics (review): Schneider
17:40! Climate and photochemistry of potentially habitable exoplanets: Tian
18:20! The prospects for characterizing the atmospheres of rocky exoplanets:
19:00! Evening break
Dorian! Abbot! University of Chicago
Miquela! Abbot! University of Chicago
Nadine! Afram! Kiepeneheuer Inst. für Sonnenphysik! p. 51
Suzanne! Aigrain! University of Oxford
Yann! Alibert! University of Bern! p. 22
David! Amundsen! University of Exeter! p. 52
Daniel! Angerhausen! Rensselaer Polytechnic Institute! p. 38
Daniel! Apai! University of Arizona
Jeremy! Bailey! University of New South Wales! p. 39
Travis! Barman! University of Arizona
Joanna! Barstow! University of Oxford! p. 14
Jean-Loup! Baudino! LESIA, Observatoire de Paris! p. 57
Jacob! Bean! University of Chicago
Thomas! Beatty! Ohio State University! p. 58
Björn! Benneke! California Institute of Technology! p. 31
Andrei! Berdyugin! FINCA, University of Turku! p. 39
Svetlana! Berdyugina! Kiepeneheuer Inst. für Sonnenphysik! p. 22
Zachory! Berta-Thompson! Massachusetts Inst. of Technology! p. 32
Jayne! Birkby! Leiden Observatory! p. 39
Jasmina! Blecic! University of Central Florida! p. 52
Kimberly! Bott! University of New South Wales! p. 52
Vincent! Bourrier! Institut d’Astrophysique de Paris! p. 40
Matteo! Brogi! Leiden Observatory! p. 40
Carolyn! Brown! University of Southern Queensland
Matthew! Browning! University of Exeter
Ben! Burningham! University of Hertfordshire! p. 58
Ludmila! Carone! CmPA, KU Leuven! p. 23
David! Charbonneau! Harvard University! p. 23
Ofer! Cohen! Harvard-Smithsonian CfA! p. 24
Vincent! Coudé du Foresto! Paris Observatory / Bern University
Nicolas! Cowan! Northwestern University! p. 32
Ian! Crossfield! Max Plank Institute for Astrophysics! p. 58
Nicolas! Crouzet! Dunlap Institute, University of Toronto! p. 41
Patricio! Cubillos! University of Central Florida! p. 41
Mario! Damasso! INAF-Astrophysical Obs. of Torino! p. 32
Remco! de Kok! SRON / Leiden Observatory! p. 41
Julien! de Wit! Massachusetts Institute of Technology! p. 42
Laetitia! Delrez! University of Liège
Brice-Olivier! Demory! Massachusetts Institute of Technology! p. 42
Jean-Michel! Desert! University of Colorado
Hannah! Diamond-Lowe! University of Chicago
Ian! Dobbs-Dixon! NYU Abu Dhabi! p. 53
Caroline! Dorn! University of Bern
Diana! Dragomir! University of California/LCOGT! p. 33
Benjamin! Drummond! University of Exeter
Siegfried! Eggl! IMCCE, Observatoire de Paris! p. 24
Lindy! Elkins-Tanton! DTM, Carnegie Institution
Justin! Erwin! University of Arizona! p. 53
Lisa! Esteves! University of Toronto! p. 43
Tom! Evans! University of Oxford! p. 43
Jacqueline! Faherty! Carnegie Institution of Washington, DTM
Sean! Faulk! University of California, Los Angeles! p. 14
Dora! Fohring! Durham University! p. 43
Doris! Folini! ETH Zürich
Jonathan! Fortney! University of California-Santa Cruz
Jonathan! Fraine! University of Maryland! p. 33
Richard! Freedman! SETI Institute
Sebastien! Fromang! CEA Saclay
Antonio! GarcÌa Muñoz! RSSD, European Space Agency! p. 19
Neale! Gibson! European Southern Observatory! p. 43
Daniel! Gisler! Kiepeneheuer Institut für Sonnenphysik! p. 15
John Lee! Grenfell! German Aerospace Centre (DLR)! p. 24
Simon! Grimm! University of Zurich! p. 53
Sandrine! Guerlet! Laboratoire de Métrologie Dynamique! p. 15
Aimee! Hall! University of Cambridge! p. 34
Joseph! Harrington! University of Central Florida! p. 44
Carole! Haswell! The Open University! p. 44
Christiane! Helling! University of St Andrews! p. 59
Kevin! Heng! University of Bern! p. 54
Klemens! Hocke! University of Bern
Jens! Hoeijmakers! Leiden Observatory
Derek! Homeier! CRAL/ENS-Lyon! p. 59
Yasunori! Hori! National Astronomical Observatory Japan! p. 34
Andrew! Howard! University of Hawaii
Renyu! Hu! California Institute of Technology! p. 34
Yongyun! Hu! Peking University! p. 25
Nicolas! Iro! Klimacampus - University of Hamburg! p. 54
Patrick! Irwin! Oxford University! p.16
Kate! Isaak! ESTEC, European Space Agency
Joshua! Kammer! California Institute of Technology! p. 35
Yohai! Kaspi! Weizmann Institute of Science
Tiffany! Kataria! University of Arizona! p. 25
Hajime! Kawahara! University of Tokyo! p. 45
Lucyna! Kedziora-Chudczer University of New South Wales! p.16
Sara! Khalafinejad! Hamburg Observatory
Flavien! Kiefer! IAP! p. 60
Cevahir! Kilic! University of Bern! p. 26
Daniel! Kitzmann! Technical University Berlin! p. 55
Heather! Knutson! California Institute of Technology
Daniel! Koll! University of Chicago! p. 36
Thaddeus! Komacek! University of Arizona! p. 55
Tommi! Koskinen! University of Arizona! p. 56
Nadia! Kostogryz! Kiepeneheuer Inst. für Sonnenphysik p.16
Laura! Kreidberg! University of Chicago! p. 36
Oleksii! Kuzmychov! Kiepeneheuer Inst. für Sonnenphysik!p. 60
Panayotis! Lavvas! CNRS (France)
Alain! Lecavelier! Institut d’Astrophysique deParis! p. 56
Jeremy! Leconte! CITA/LMD! p. 26
Jae-Min! Lee! University of Zurich! p. 60
Emmanuel! Lellouch! Observatoire de Paris
Stephen! Lewis! The Open University! p. 17
Michael! Line! University of California-SC! p. 61
Jeffrey! Linsky! University of Colorado
Michael! Liu! University of Hawaii! p. 61
Joe! Llama! University of St Andrews! p. 45
Eric! Lopez! UC Santa Cruz! p. 36
Roxana! Lupu! SETI Institute! p. 27
Nikku! Madhusudhan! University of Cambridge! p. 37
Jared! Males! University of Arizona! p. 61
Luigi! Mancini! Max Planck Insitute for Astronomy
Avi! Mandell! NASA Goddard! p. 46
Nadejda! Marounina! Laboratoire de Planetologie, Nantes! p. 17
Stephen! Marsden! University of Southern Queensland! p. 27
Nathan! Mayne! University of Exeter! p. 56
Victoria! Meadows! University of Washington
Joao! Mendonca! University of Bern! p.18
Kristen! Menou! Columbia University
Stephen! Messenger! Massachusetts Inst.of T echnology
Stanimir! Metchev! University of Western Ontario! p. 62
Alison! Mitchell! University of Californa LA
Jonathan! Mitchell! University of Californa LA
Pilar! Montanes-Rodriguez Inst. de Astrofisica de Canarias! p. 18
Caroline! Morley! University of California-Santa Cruz! p. 62
Katie! Morzinski! University of Arizona! p. 62
Julie! Moses! Space Science Institute
Norio! Narita! National Astronomical Obs. Japan! p. 37
Nikolay! Nikolov! University of Exeter! p. 46
Lisa! Nortmann! Institut für Astrophysik Göttingen! p. 47
Joseph! O'Rourke! California Institute of Technology! p. 47
James! Owen! CITA! p. 48
Hannu! Parviainen! University of Oxford! p. 48
Enric! Palle! Instituto de Astrofisica de Canarias! p. 48
Raymond! Pierrehumbert!University of Chicago
Frédéric! Pont! University of Exeter
Max! Popp! Max Planck Institute for Meteorology! p. 28
Ramses! Ramirez! Pennsylvania State University
Peter! Read! University of Oxford! p. 19
Tyler! Robinson! NASA Ames Research Center! p. 20
Leslie! Rogers! California Institute of Technology! p. 37
Tamara! Rogers! University of Arizona
Sarah! Rugheimer! Harvard University
Josiane! Salameh! Max Planck Institute for Meteorology! p. 28
Tapio! Schneider! ETH Zürich
Henriette! Schwarz! Leiden Observatory! p. 49
Aomawa! Shields! University of Washington! p. 29
Adam! Showman! University of Arizona
Avi! Shporer! Caltech/JPL! p. 49
David! Sing! University of Exeter
Andrew! Skemer! University of Arizona! p. 63
Kevin! Stevenson! University of Chicago! p. 50
Paul! Tackley! ETH Zürich
Zhihong! Tan! Caltech/JPL! p. 29
Feng! Tian! Peking University! p. 29
Kamen! Todorov! ETH Zürich! p. 50
Pascal! Tremblin! University of Exeter
Vincent! Van Eylen! Aarhus University! p. 50
Tamas Norbert ! Varga! Eötvös Lorand University
Giovanni! Vladilo! INAF-Astrophysical Obs. of Torino
Hannah! Wakeford! University of Exeter! p. 51
Yuwei! Wang! Peking University
Paul Anthony! Wilson! University of Exeter! p. 63
Peter! Woitke! University of St Andrews! p. 57
Robin! Wordsworth! University of Chicago! p. 30
Peter! Wurz! University of Bern! p. 20
Aurélien! Wyttenbach! University of Geneva! p. 38
Fei! Yan! ESO! p. 21
Jun! Yang! University of Chicago! p. 30
Angela! Zalucha! SETI Institute! p. 21
Robert! Zellem! University of Arizona! p. 51
Andras! Zsom! Massachusetts Institute of Technology! p. 31
TALKS/POSTERS ABSTRACTS *
INSIGHTS FROM SOLAR SYSTEM PLANETS
Gloomy planets: overcoming remote sensing challenges for cloudy atmospheres
Joanna K. Barstow — University of Oxford
For most known planets, our only knowledge about their atmospheres comes from remote
sensing and spectroscopic analysis. There are often multiple, degenerate atmospheric
states that could produce the observed spectra, and usually more complex atmospheric
models result in greater numbers of permitted atmospheric states. The inclusion of clouds
in an atmospheric model increases its complexity. The size of the cloud parameter space,
the nature of the condensate, size of condensate particles, number density and location
within the atmosphere all influence spectral features.
Recent analyses of the best-studied extrasolar planets, such as HD 189733b and GJ
1214b, indicate that clouds are as ubiquitous outside the solar system as they are inside it.
Their probable presence on these planets can no longer be ignored, but the quality and
spectral coverage of remote sensing data for exoplanets and the outer planets in our own
solar system limits our ability to draw conclusions about their nature. We are left with a
vast, underconstrained model parameter space to explore. In addition, the presence of
uncharacterised clouds in planetary atmospheres can prevent us from placing constraints
on temperature structure and chemistry due to model degeneracy, or can result in
mistaken conclusions based on incorrect assumptions.
I explore the significance of different cloud properties for reflection, emission and
transmission spectra of planetary atmospheres, including examples such as the extremely
detailed characterisation of the H2SO4 cloud on Venus, the hints of enstatite clouds on HD
189733b, and the possibility of Titan-like hydrocarbon hazes on GJ 1214b. I will present
suggestions for a framework to explore cloudy solutions for data-poor planets.
The structure of the Intertropical Convergence Zone over a wide range of
atmospheric circulations simulated with an idealized GCM!
Sean Faulk — UCLA!
One of the most prominent features of the Earth's large-scale circulation in low latitudes is
the intertropical convergence zone (ITCZ), where tropical precipitation is concentrated in a
relatively narrow latitudinal band. Given that small changes in the ITCZ can result in large
local changes in precipitation, factors that control its structure and position have been
widely investigated in the literature. In other planetary settings such as Mars and Titan, it
has been argued that an ITCZ can migrate significantly off the equator into the summer
hemisphere, perhaps even to the summer pole. The dynamical, thermodynamical and
radiative mechanisms controlling seasonal ITCZ migrations has only begun to be explored.
Exploration of the ITCZ behavior in a wide parameter space is important to understand the
fundamental dynamics of the Earth's ITCZ and also to characterize climates on other
planets. Here, we examine the structure of the ITCZ over a wide range of atmospheric
* Arranged by topic in six categories. See the list of participants (p.10) to find page of specific abstract
circulations with an idealized General Circulation Model (GCM), in which an atmospheric
model with idealized physics is coupled to an aquaplanet slab ocean of fixed depth and the
top-of-atmosphere insolation is varied seasonally. A broad range of circulation regimes is
studied by changing the thermal inertia of the slab ocean, the planet rotation rate and
radius while keeping the seasonal cycle of insolation fixed. The climates of Earth, Mars
and Titan will be discussed in this context, and implications for classifying exoplanet
climates will be drawn.
A search for hot water vapor in the atmosphere of Venus during the 2012 transit
Daniel Gisler — Kiepenheuer-Institut für Sonnenphysik
We have observed the Venus transit in 2012 using the Scatter-free Observatory for Limb
Active Regions and Coronae (SOLARC), located on the summit of Haleakala, Maui. The
SOLARC is a 45 cm off-axis Gregorian telescope. This telescope design minimizes
scattered light, that is critical for photon-limited observations. The data has been collected
with the Optical Fiber Imaging Spectralpoarimeter (OFIS). Our goal is to search for water
vapor lines absorbing solar light passing through the Venusian atmosphere and evaluate
the sensitivity of our spectropolarimetric technique to detect water and other constituents
in atmospheres of transiting exoplanets. Here we present the data and analyze Stokes I,
Q, U spectra extracted from the solar disk and the Venus limb and night side. We estimate
limits on the water vapor partial pressure and compare these with measurements by space
missions and probes.
Development of a new Global Climate Model of Saturn's stratosphere
Sandrine Guerlet — Laboratoire de Météorologie Dynamique, Paris!
Recent observations of Saturn’s stratospheric thermal structure and composition have
revealed new phenomena: an equatorial oscillation in temperature, reminiscent of the
Earth's Quasi-Biennal Oscillation ; strong meridional contrasts of hydrocarbons ; a warm
“beacon” associated with the powerful 2010 storm. Those signatures cannot be
reproduced by 1D photochemical and radiative models and suggest that atmospheric
dynamics plays a key role. This motivated us to develop a complete 3D General
Circulation Model (GCM) for Saturn, based on the LMD’s hydrodynamical core, to explore
the circulation, seasonal variability, and wave activity in Saturn's atmosphere.
In order to closely reproduce Saturn's radiative forcing, a particular emphasis was put in
obtaining fast and accurate radiative transfer calculations. Our radiative model uses
correlated-k distributions and spectral discretization tailored for Saturn's atmosphere. We
include an internal heat flux, ring shadowing and both tropospheric and stratospheric
Firstly, we will present a comparison of temperature fields obtained with this new
seasonal, radiative equilibrium model to that inferred from Cassini/CIRS observations.
Even in the absence of dynamics, our model qualitatively reproduces the overall
meridional temperature gradient between the summer and the winter hemispheres in the
lower stratosphere except in the equatorial region, where the temperature structure is
governed by the dynamical equatorial oscillation. Our model can also reproduce the
“temperature knee” observed around 200 mbar, which is caused by heating at the top of
the tropospheric aerosol layer.
Finally, we will show GCM simulations coupling the 3D dynamical core to this radiative
model, and discuss the large-scale stratospheric circulations driven by the radiative
Simulated transit spectra of Earth and Jupiter
Patrick Irwin — University of Oxford
In recent years, increasingly accurate measurements have been made of the transit
spectra of hot Jupiters, such as HD 189733b, from the visible through to mid-infrared
wavelengths. These have been modelled to derive the likely atmospheric structure and
composition of these planets. As measurement techniques improve, the transit spectra of
super-Earths such as GJ 1214b are becoming increasingly accessible, allowing model
atmospheric states to be fitted for this class of planet also. While it is not yet possible to
constrain the atmospheric states of solar system-like planets such as the Earth or Jupiter
from such measurements, it is hoped that this might one day become practical; if so, it is of
interest to determine what we might infer from such measurements. In this work we have
constructed atmospheric models of Earth and Jupiter from 0.2 - 15 microns that are
consistent with ground-based and satellite observations. From these models we calculate
the primary and secondary transit spectra (with respect to the Sun) that would be observed
by a remote observer, many light years away, and also directly imaged spectra, assuming
that this one day becomes technically feasible. From these spectra we test how well
optimal estimation retrieval models can determine the atmospheric states and compare
these with the “ground truths” in order to assess: a) the inherent difficulty in using transit
spectra observations to observe solar system-like targets; b) the relative merits of primary
versus secondary transit spectra; and c) the optimal wavelength coverage, resolutions and
sensitivities required to retrieve useful information about the atmospheres of such planets.
D/H ratios in methane in the atmosphere of giant planets and Titan!
Lucyna Kedziora-Chudczer — University of New South Wales
We present observations of the GNIRS/GEMINI high resolution spectra at 1.58 and 2.03
microns for the giant planets of our Solar System and Saturn's moon Titan. We fitted the
atmospheric absorption spectra of these objects using the VSTAR line-by-line radiative
transfer modelling to estimate the D/H ratios from deuterated methane in both bands.
Deuteration of the outer planets can be used not only as a diagnostic of initial conditions in
the solar nebula during formation of giant planets but also to help to determine the location
at which planets accreted the bulk of their mass. We estimated that based on D/H ratio
derived for Titan, the Saturnian system formed close to its current location, which has
implication on previously proposed migration theories.
Vertical structure of gas-planet atmospheres inferred from methane bands
Nadiia Kostogryz — Kiepenheuer-Institut für Sonnenphysik
Visible and near infrared spectra of the Jovian planets in the Solar system are dominated
by methane absorption features. These bands are very useful for determining the vertical
cloud structure of planetary atmospheres as was proposed by Morozhenko (1984) and
implemented for the Uranus atmosphere by Kostogryz (2013). The fact that the diffusely
reflected radiation is formed at different effective depths in the atmosphere allows to
constrain the vertical cloud structure. The cloud height and opacity strongly influence the
geometric albedo of the planet and, therefore, are needed for constructing a realistic
atmosphere model. Here we extend this method to exoplanetary atmospheres. We
simulate methane spectra from atmospheres with various cloud structure and analyze
them as observed spectra to infer the cloud properties. We investigate limits on the
spectral resolution and signal-to-noise ratio for this technique to be applied to hot Jupiter
Atmospheric super-rotation in solar system and extra-solar planetary atmospheres
Stephen R. Lewis — The Open University, UK
Super-rotation is a common phenomenon in solar system planetary atmospheres. Out of
the four substantial atmospheres possessed by solid bodies in the solar system, the slowly
rotating planet, Venus, and moon, Titan, are both well-known to have atmospheres that
rotate on average substantially more quickly than does the solid surface underneath. The
more rapidly rotating planets, Mars and Earth, have much weaker global super-rotation,
but both can exhibit time-varying prograde jets near the equator which rotate more rapidly
than the local surface. Atmospheric super-rotation is not restricted to planets with solid
surfaces and shallow atmospheres. Cloud-tracking observations of the gas giants Jupiter
and Saturn show that they both possess rapid prograde equatorial jets and hence exhibit
Simplified global circulation models of extra-solar planets, including representations of
hot Jupiters and Earth-like planets rotating at different rates, can also show sustained
super-rotating equatorial jets in different dynamical regimes. In the extra-solar planet
cases in particular, the quantitative results are highly sensitive to model parameters.
In each case the detailed mechanism, or combination of mechanisms, which produces
the super-rotating jets might vary, but all require longitudinally asymmetric motions, waves
or eddies, to transport angular momentum up-gradient into the jets. The mechanism is not
always easy to diagnose from observations and requires careful modelling. We review
both observations of solar system planets and recent global circulation model results,
combined in the case of Mars and Earth in the form of atmospheric reanalyses by data
assimilation, together with simplified extra-solar planet simulations.
Generation and early evolution of Titan's atmosphere
Nadejda Marounina! — LPGN!
Titan is the only satellite of the Solar System with a substantial atmosphere (1.47 bar),
which is primarily composed of N2 (~98%) and CH4 (~ 2%). The low Ar/N2 ratio measured
by the Huygens probe in Titan's atmosphere indicates that the nitrogen was incorporated
as NH3 and possibly other nitrogen-bearing easily condensible compounds. Therefore, a
conversion mechanisms is needed to explain the present-day N2-dominated atmosphere.
Different conversion scenarios have been proposed (endogenic conversion, atmospheric
impact chemistry...). Here we evaluate a scenario recently proposed by Sekine et al.
(2011) involving an impact-induced conversion of NH3, stored as hydrate in Titan’s icy
crust, and subsequent degassing of N2 during the Late Heavy Bombardement. Using the
scaling laws derived from their experimental study, we computed the balance between the
degassed N2 and the erosion of the atmosphere by impact (Shuvalov 2009) for an impact
population characteristic of the Late Heavy Bombardment (LHB). Our numerical model
include a parameterized description of the radiative and thermodynamical equilibria of the
atmosphere (Lorenz et al. 1999).
Our results show that whatever the size of NH3-enriched crustal reservoirs, N2 production
by impacts is not able to counterbalance the atmospheric loss by impact erosion for
realistic size distribution of impactors. We show that in order to preserve a substantial
atmosphere on Titan after the LHB, an initially massive atmosphere (5-times present-day
mass) is required. Our results indicate that a very efficient conversion mechanism should
have occurred during the accretion and shortly after to produce such a massive N2
During accretion the impact heating may have been strong enough to melt the superficial
icy layer and form an ocean, which volatile species outgassed and form a primitive
atmosphere (Monteux et al., in prep). We are currently developing a new numerical model
of a liquid-vapor equilibrium for various initial oceanic composition to investigate how a
massive atmosphere may be generated during the satellite growth and how it may then
evolve toward a composition dominated by N2. More generally, our model may address
how atmosphere may be generated in water-rich objects, which may be common around
Simulating the atmospheric circulation of Venus!
Joao Mendonca — University of Bern!
Venus is the most Earth-like astronomical object in terms of size, mass and orbital
properties in our Solar system. Despite these similarities, Venus is slowly rotating in the
opposite direction, has the most massive atmosphere of the terrestrial planets and is
covered by an opaque and highly reflective cloud layer. These differences are important to
drive the Venus atmospheric circulation to a very distinct regime from Earth's, with strong
atmospheric super-rotation and a variety of other atmospheric dynamic features such as
the observed large-scale wave patterns, which are not well understood.
I will summarise the main efforts of the last three decades to simulate the Venus
atmospheric circulation using general circulation models, and the most likely mechanisms
driving the atmosphere to the actual observed circulation. Recently in Lebonnois et al.
2011, it was shown that Venus general circulation models that use simplified
representations of heating, cooling and friction processes, obtained very distinct results,
which raised concerns about the intrinsic numerical errors and assumptions in the routines
that solve the dynamical behaviour of the flow. These problems and the latest results by
modern models, which use more physically-based parameterizations (Lebonnois et al.
2010 & Mendonca 2013) will be discussed and compared. In our new model (Mendonca
2013), the Venus atmospheric circulation in the cloud region is well represented.
Additionally, the results are sensitive to some radiative properties near the surface and
also to the amount of clouds. Despite the progress, there are still modelling difficulties
which I will address in this work. I will also analyse and describe the main implications that
the Venus climate modelling has in the exploration of exo-climes.
Transmission spectra of Jupiter from Ganymede during eclipses!
Pilar Montañès-Rodrìguez — Instituto de Astrofìsica de Canarias !
Transit spectroscopy data from several hot Jupiter planets are already being collected from
several space and ground-based instruments. And more temperate Jupiter-like planets are
expected to be characterized in the near future. In this framework, an investigation of the
spectral features of Jupiter, in transmission, as if it were observed from a distant star, can
greatly contribute to the modeling efforts of such planetary atmospheres. Here, we present
observations of the near-infrared transmission spectrum of Jupiter with LIRIS at the WHT,
as reflected from Ganymede's surface during an eclipse. When Ganymede is in the umbra
of Jupiter, only sunlight that has traversed the Jupiter atmosphere is illuminating its
surface. By taking observations of Ganymede before and during an eclipse, we are able to
retrieve Jupiter's atmospheric fingerprints.
Disk-integrated reflection light curves of planets!
Antonio Garcìa Muñoz — ESA-RSSD, ESTEC
The light scattered by a planet atmosphere contains valuable information on the planet’s
composition and aerosol content. Typically, the interpretation of that information requires
elaborate radiative transport models accounting for the absorption and scattering
processes undergone by the star photons on their passage through the atmosphere. I
have been working on a particular family of algorithms based on Backward Monte Carlo
(BMC) integration for solving the multiple-scattering problem in atmospheric media. BMC
algorithms simulate statistically the photon trajectories in the reverse order that they
actually occur, i.e. they trace the photons from the detector through the atmospheric
medium and onwards to the illumination source following probability laws dictated by the
medium’s optical properties. BMC algorithms are versatile, as they can handle diverse
viewing and illumination geometries, and can readily accommodate various physical
phenomena. As will be shown, BMC algorithms are very well suited for the prediction of
magnitudes integrated over a planet’s disk (whether uniform or not). Disk-integrated
magnitudes are relevant in the current context of exploration of extrasolar planets because
spatial resolution of these objects will not be technologically feasible in the near future. I
have been working on various predictions for the disk-integrated properties of planets that
demonstrate the capacities of the BMC algorithm. These cases include the variability of
the Earth’s integrated signal caused by diurnal and seasonal changes in the surface
reflectance and cloudiness, or by sporadic injection of large amounts of volcanic particles
into the atmosphere. Since the implemented BMC algorithm includes a polarization mode,
these examples also serve to illustrate the potential of polarimetry in the characterization
of both Solar System and extrasolar planets. The work is complemented with the analysis
of disk-integrated photometric observations of Earth and Venus drawn from various
Comparative global energy budgets for the climates of terrestrial and gas giant
Peter Read — University of Oxford
The weather and climate on Earth are generally determined by the amount and distribution
of incoming solar radiation. This must be balanced in equilibrium by the emission of
thermal radiation from the surface and atmosphere, but the precise routes by which
incoming energy is transferred from the surface, through the atmosphere and back out to
space are important features that characterize the current climate. This has been analysed
by several groups over the years, based on combinations of numerical model simulations
and direct observations of the Earth’s climate system. The results are often presented in
schematic form (Trenberth et al. 2009) to show the main routes for the transfer of energy
into, out of and within the climate system. Although relatively simple in concept, such
diagrams convey a great deal of information about the climate system in a compact form,
and are especially valuable pedagogically at school and undergraduate level.
Such an approach has not so far been adopted in any systematic way for other planets of
the Solar System, let alone beyond, although quite detailed climate models of several
planets are now available, constrained by many new observations and measurements.
Here we analyse the global transfers of energy within the climate systems of a range of
terrestrial planetary bodies within the Solar System, including Mars, Titan and Venus, as
simulated by relatively comprehensive numerical circulation models. These results will
then be presented in schematic form for comparison with the “classical” global energy
budget analysis of Trenberth et al. for the Earth, highlighting the important similarities and
differences. We also consider how to extend this approach towards other Solar System
and extra-solar planets, including Jupiter, Saturn and hot Jupiter exoplanets.
A ~0.1 bar Rule for Tropopause Temperature Minima in Thick Atmospheres of
Planets and Large Moons
Tyler Robinson — University of Washington
Tropopause temperature minima are fundamental for understanding planetary atmospheric
structure. Inversions in the stratospheres of Earth, Jupiter, Saturn, Titan, Uranus, and
Neptune lead to temperature minima that, remarkably, all occur near 0.1 bar, despite very
different insolation, atmospheric composition, gravity, and internal heat flux. We have
explored this common 0.1 bar tropopause using an analytic 1-D radiative-convective
model. We find that tropopause temperature minima always lie in the radiative regime,
above the radiative-convective boundary. Thus, the shared 0.1 bar tropopause arises from
the common physics of radiative transfer. Model fits to solar system worlds show that the
gray infrared optical depth where the tropopause minimum occurs is ~0.1. Furthermore,
the gray infrared optical depths at a pressure of 1 bar are typically of order a few. These,
along with a commonly used power-law scaling between pressure and optical depth, set
the tropopause pressure at ~0.1 bar. Moving beyond the solar system, we show that the
typical gray infrared optical depth of the tropopause minimum is ~0.1 for a wide range of
plausible atmospheric compositions. This optical depth marks the transition into an upper
region of an atmosphere that is very transparent to thermal radiation. Here, shortwave
absorption can dominate the temperature profile and, thus, create an inversion and
corresponding temperature minimum. These findings imply that the common 0.1 bar
tropopause levels seen in the solar system atmospheres are more universal. Thus, we
hypothesize that many exoplanets will possess a 0.1 bar tropopause temperature
Measurement of the atmospheres of Europa, Ganymede, and Callisto
Peter Wurz — Physics Institute, University of Bern!
The regular Jovian satellites are believed to be formed at the end of Jupiter's formation
epoch, from the collisional accretion of solids originating in the Solar Nebula, and captured
in a disk orbiting around the planet. The solids taking part to the formation of the satellites
therefore originate from the initial protoplanetary disk, and have probably experienced
lower temperature and pressure conditions as has the material incorporated in Jupiter, and
their chemical composition has been probably less altered. By measuring the composition
of the Jovian satellites, it is therefore possible to set constraints on the chemical
composition of building blocks of planets and satellites, and ultimately on the
thermodynamical conditions in the Solar Nebula.
The Particle Environment Package (PEP) suite has been selected for the JUICE mission
of ESA, which contains instruments for the comprehensive measurements of electrons,
ions and neutrals. One of the instruments is the Neutral and Ion Mass spectrometer
instrument (NIM). NIM is a time-of-flight neutral gas and thermal ion mass spectrometer
optimised for exospheric investigations. NIM will measure the composition of the
exospheres of Europa, Ganymede, and Callisto. Various physical processes are acting on
the surfaces of Jupiter’s icy moons to promote material from the surface into the
exosphere. These are thermal desorption (sublimation), photon stimulated desorption, ioninduced
sputtering, and micro-meteorite impact vaporisation, with sputtering being the
most important surface release process. Sputtering releases all species present on the
surface more or less stoichiometrically into the exosphere, allowing deriving the chemical
composition of the surface from these measurements. However, the chemical composition
of the surface is modified by the bombardment of energetic electrons and ions, and
ultraviolet radiation, which has to be accounted for in the chemical analysis.
High-resolution and high-SNR transmission spectrum of Earth’s atmosphere
obtained from a lunar eclipse!
Fei Yan — European Southern Observatory & National Astronomical Observatories,
Chinese Academy of Sciences!
With the rapid developments in the exoplanet field, more and more terrestrial exoplanets
are being detected. Characterising their atmospheres using transit observations will
become a key datum in the quest for detecting an Earth-like exoplanet. The atmospheric
transmission spectrum of our Earth will be an ideal template for comparison with future
exo-Earth candidates. By observing a lunar eclipse, which offers a similar configuration to
that of an exoplanet transit, we have obtained a high resolution and high signal-to-noise
ratio transmission spectrum of the Earth’s atmosphere.
We will present the transmission spectrum together with our 1-D atmospheric spectral
model. From the model-fit, the column densities of the various atmospheric species are
calculated. Some intersting results from this work are discussed, such as the forwardscattered
sunlight, the oxygen isotopes, the souces of NO2.
Extreme Planetary Classes in Our Own Solar System: The Atmospheric Circulation
of Pluto and Triton!
Angela Zalucha — SETI Institute!
Pluto and Triton (Neptune's largest moon) are often called “sister worlds” due to their
nearly identical atmospheric composition, size, and temperature. While the bulk
temperature and composition have been constrained by ground-based stellar occultation
observations and the Voyager 2 flyby of Neptune, the circulation patterns at all scales are
still not known due to the difficulty in observing wind remotely. Pluto and Triton, or “ice
dwarfs”, are quite unusual compared with other known planetary bodies, in that efficient
methane absorption in the atmosphere creates at strong temperature inversion
(temperature increasing with height) near the surface that has been dubbed the
stratosphere. Such a configuration is extremely stable and prevents vertical motion, which
impacts flow in the other directions as well (for example, Hadley cells, ubiquitous on
terrestrial planets and perhaps super-Earths, are not expected to exist). Moreover, much
like Mars, it is thought that these sister worlds have a volatile cycle where the main
atmospheric constituent (here molecular nitrogen) condenses and sublimates throughout
the year, even to the point of atmospheric collapse.
Within the past few years, there has been a surge of interest in Pluto's global circulation
patterns. This problem has posed a challenge unprecedented from other planetary bodies.
First, Pluto's year is about 250 Earth years, requiring long simulation times.Second, Pluto's
atmosphere and surface are thought to be strongly coupled radiatively, requiring both a
sophisticated atmosphere and surface model. The properties (emissivity, configuration of
ices, thermal inertia, and total surface ice inventory) of Pluto's surface are not well
constrained. Various groups have used different general circulation models (GCMs) to
predict the atmospheric circulation of Pluto. I will discuss results from the MIT Pluto GCM,
which after several years of atmosphere-only studies (e.g. Zalucha and Michaels 2013) is
now coupled to a sophisticated surface model.
Maximum planet size for habitability
Yann Alibert! — University of Bern
The conditions that a planet must fulfill in order to be habitable are not precisely known.
However, it is comparatively easier to define conditions under which a planet is very likely
not habitable. Finding such conditions is moreover important as it can help to select, in an
ensemble of potentially observable planets, which ones should be observed in more
details for characterization studies. Assuming, as in the case of the Earth, that the
presence of a C-cycle is a necessary condition for long-term habitability, we derive, as a
function of the planetary mass, a radius above which a planet is likely not habitable. For
this, we compute the maximum radius a planet can have in order to fulfill two constraints:
surface conditions compatible with the existence of liquid water, and no ice layer at the
bottom of a putative global ocean. We demonstrate that, above a given radius, these two
constraints cannot be met. For this, we compute internal structure models of planets, using
a 5-layer model (core, inner mantle, outer mantle, ocean and atmosphere), for different
masses and composition of the planets (in particular Fe/Si ratio of the planet). Our results
show that for planets in the Super-Earth mass range (1-12 Mearth), the overall maximum
size that a planet can have varies between 1.8 and 2.3 Rearth. This radius is reduced when
considering planets with higher Fe/Si ratios, and taking into account irradiation when
computing the gas envelope structure.
Remote detection of biosignatures on Earth-like planets
Svetlana Berdyugina — KIS, Freiburg
Life on Earth is aware of light polarization and makes good use of it for its survival and
growth. In all cases, it is the solar light that is reflected, processed and analyzed by life
forms, and the same circumstances are expected to exist on all habitable planets.
Photosynthesis, in particular, is very likely to arise on another planet and can produce
conspicuous biosignatures. Recently, it was demonstrated that polarized reflected light can
be detected from exoplanetary atmospheres. We focus now on identifying biological
polarization effects, e.g., selective light absorption or scattering by biogenic molecules.
This helps to enhance the reliability of other biomarkers for distant detection of life which
can be contaminated by non-biological sources. Here we present a laboratory study of
reflected light polarization from various terrestrial plants and non-biological samples (rocks
and sands). We use these measured reflection spectra to synthesize polarized spectra of
Earth-like planets with various contributions from the land, photosynthetic organisms,
ocean, atmosphere, and clouds. We estimate the required photometric and polarimetric
sensitivity to detect such planets in habitable zones of nearby stars.
Weather on strange new worlds: Large scale atmospheric dynamics on tidally
locked terrestrial planets around an M dwarf star
Ludmila Carone — KU Leuven, Center for mathematical Plasma-astrophysics
It is likely that the first habitable extrasolar planet with an atmosphere will be discovered
around an M star. Indeed, several terrestrial planets have already been discovered around
such stars. These planets will probably be tidally locked. Therefore, the climate dynamics
of a terrestrial exoplanet — even in the habitable zone — might be very different from the
Earth. Firstly, the rotation will be slower and we would therefore not expect mid-latidude
cyclones but rather a barotropic atmosphere. Secondly, the temperature varies rather with
longitude than with latitude leading to circulation between the dark and cold hemisphere.
Because there are many unknowns with exoplanets, in particular with terrestrial
exoplanets, we decided to explore the dynamics of a greenhouse atmosphere on a tidally
locked planet with a medium-size parameter study. We used an idealized global threedimensional
dry circulation model (GCM) with an idealized forcing, adopting MITgcm
(http://mitgcm.org). As a first step, different day-night temperature differences, rotation
periods, time scales for radiation and surface friction, and surface pressures were
investigated. The emerging large scale dynamics of the atmosphere was compared with
previous studies and with observations and models of Venus and Titan; the latter being the
closest analogues in the Solar System. Our goal is to identify, on the one hand, features
that are robust against parameter change — like superrotation and Hadley-like circulation
cells — and, on the other hand, to investigate climate patterns that vary strongly with
different assumptions: like the surface wind and temperature, and large scale vortices.
This not only broadens our understanding about the different mechanisms at play in
atmospheres, but may also lead to a better coupling between observations of transiting
terrestrial exoplanets and atmospheric models.
The Prospects for Characterizing the Atmospheres of Rocky Exoplanets!
David!Charbonneau — Harvard University!
The coming decade brings the promise of direct spectroscopic characterization of the
atmospheres of rocky planets orbiting other nearby stars. The most accessible planets will
be those that orbit M-dwarfs, owing to the diminutive stature, low-luminosities, and
preponderance of these stars. This talk will present a quantitative evaluation of the
prospects for this path informed by the most recent data: I will begin by presenting an
analysis of the complete Kepler dataset to determine the rate of occurrence of such
planets. I will combine this with the catalog of nearby stars to evaluate the likely distance
to the closest transiting systems, and the likely characteristics of the stellar host. I will then
address the sensitivity of the NASA TESS Mission, the MEarth transit survey, and other
ongoing projects to detect such objects. I will conclude by presenting the likely signal-tonoise,
resolution, and wavelength coverage that should be delivered by the James Webb
Space Telescope, the Giant Magellan telescope, and other large ground-based
telescopes. Using the technique of transmission spectroscopy, some of these telescopes
should be able to investigate such planetary atmospheres beginning as early as 2018,
provided the community has identified the targets. The goal of this presentation will be to
leave the audience with a quantitative understanding of what we can, and cannot, hope to
measure in this time frame, and thus to assist them in directing their research efforts
Exoplanetary Extreme Space Weather
Ofer Cohen — Harvard-Smithsonian CfA!
Exoplanetary research is driven by the ultimate goal of defining whether life can exist
beyond the Earth and the solar system, while recent searches for exoplanets are focused
increasingly on detecting rocky, Earth-like planets around M-dwarf stars, which are by far
the most numerous type of star in the Universe. The “planet habitability” problem is a
cross-disciplinary topic where commonly, a planet is defined as habitable if its surface
temperature allows water to exist in a liquid form. However, there are other factors that can
impact planet habitability. M-dwarf stars are very active magnetically and their X-ray and
ultraviolet radiation in their habitable zones is much higher than we experience near the
The physics of the solar atmosphere, the interplanetary environment, and the upper
atmospheres of planets in the solar system, including the Earth, is governed by the
radiation environment, electromagnetic forces, and the interaction between charged
particles and magnetic fields. In particular, the atmosphere of the Earth is shielded from
the intense radiation in space and from the solar wind by the Earth’s intrinsic magnetic
field. Here we present a set of numerical models, which were developed to study solar
system objects, and their application to exoplanetary, M-dwarf systems. These models
include detailed physical processes that are known to be important for solar system
bodies, but are commonly neglected in the context of exoplanets. Specifically, we
investigate the role of the planetary magnetic field in shielding the planetary atmosphere
from erosion by the extreme space environment in which it resides. Our study estimates
what planetary field strengths are necessary for protection from the caustic space
environment of M-dwarfs, and demonstrates how coronal mass ejections from M-dwarfs
affects the planet’s magnetospheres, and how much atmosphere is likely to be stripped
away in the larger events.
Defining Habitable Zones in Gravitationally Interacting Systems!
Siegfried Eggl — IMCCE Observatoire de Paris!
Calculating the extent of liquid-water habitable zones around main sequence stars
becomes challenging for systems with more than two gravitationally interacting bodies,
since the evolution of planetary orbits has to be taken into account. Given the recent
progress in determining liquid-water habitable zones within binary star systems we present
a generalized methodology to identify habitable-zone boundaries in multistar and
Planning follow-up Space Missions searching for Atmospheric Spectral
Biosignatures from a sample of potentially habitable Earth-like Exoplanets!
John Lee Grenfell — Planetary Research Inst. DLR Berlin!
Next generation missions which aim at the atmospheric characterization of rocky
extrasolar planets could provide initial information on the amounts of carbon dioxide and
water molecules in the atmospheres of hot to temperate Super-Earths. Follow-up studies
may be needed however to search for (likely weaker) atmospheric biosignature signals
from a sample of Super-Earths. Until now, most studies have focused on the effects of
atmospheric carbon dioxide and water upon planetary climate, hence (potential)
habitability. There is, however, potentially additional information held in such data. On
Earth, atmospheric carbon dioxide is strongly affected by life itself (e.g. vegetation
enhances weathering) so that on a “dead Earth” the atmospheric carbon dioxide would be
significantly higher than on its living counterpart. This could represent an additional
selection procedure for follow-up studies searching for biosignatures from a sample of
habitable planets. A difficult challenge when applying such a technique is to constrain
abiotic processes affecting atmospheric carbon dioxide e.g. hydrology, geochemistry and
outgassing. Life itself may also regulate the carbon-silicate cycle, hence stabilize climate,
but the extent and means of this process if it exists are not well known. Forty years ago a
cluster of studies focused on “live” and “dead” Earths in the context of the Gaia hypothesis
and the effect on the carbon cycle. There is now a need to revisit this work with newgeneration
models but with a focus on exoplanetary habitability. In this work we discuss
possible selection procedures for follow-up studies which search for biosignatures given a
sample of rocky Super-Earths with known atmospheric carbon dioxide and water
abundances. We apply a radiative column model to calculate consistent CO2 and H2O
abundances for dead Earth scenarios.
The role of ocean heat transport in climates of tidally locked exoplanets around M-
Yongyun Hu! — Peking University!
The distinctive feature of tidally locked exoplanets is the very uneven heating by stellar
radiation between the dayside and nightside. Previous work has focused on the role of
atmospheric heat transport in preventing atmospheric collapse on the nightside for
terrestrial exoplanets in the habitable zone around M-dwarfs. In the present paper, we
carry out the first simulation with a fully coupled atmosphere-ocean general circulation
model (AOGCM) to investigate the role of ocean heat transport in climate states of tidally
locked habitable exoplanets around M-dwarfs. Our simulation results demonstrate that
ocean heat transport substantially extends the area of open water along the equator,
showing a lobster-like spatial pattern of open water, instead of an “eyeball”. For sufficiently
high-level greenhouse gases or strong stellar radiation, ocean heat transport can even
lead to complete deglaciation of the nightside. Our simulations also suggest that ocean
heat transport likely narrows the width of M-dwarfs’ habitable zone. This study provides the
first demonstration of the importance of exo-oceanography in determining climate states
and habitability of exoplanets.
Updates to the SPARC/MITgcm: Modeling the atmospheric circulation of terrestrial
Tiffany Kataria — University of Arizona
As the detection and characterization of exoplanets moves toward smaller planets in the
super-Earth and terrestrial regimes, atmospheric circulation modeling continues to play an
important role in helping to understand ground-and space-based observations of their
atmospheres. These models must range from planets with thick atmospheric envelopes
and no surface (for super Earths) to planets with thinner atmospheres and rocky surfaces
(for terrestrial exoplanets). To that end, we present a summary of terrestrial planet updates
to our model, the Substellar and Planetary Atmospheric Radiation and Circulation
(SPARC) model, which couples the MIT General Circulation Model with a two-stream, nongrey
implementation of the multi-stream, non-grey radiative transfer code developed by
Marley and McKay (1999). These updates include an implementation of moist and dry
convective schemes, a boundary layer scheme, and a surface energy balance which self-
consistently calculates the ground temperature. We present early results from studies
looking at the role of clouds on the dynamics and habitability of terrestrial exoplanets
orbiting M-dwarfs. Using these models, we will identify fundamental dynamical
mechanisms that drive their atmospheres and constrain their thermal structures, which will
inform future observations of transiting terrestrial exoplanets, particularly at secondary
Modeling of Habitable Planets - the Underlying Atmospheric Dynamics
Cevahir Kilic! — University of Bern!
Instrumentation to detect new planets develops continually and enabled the scientific
community to characterize exoplanets in terms of physical parameters, such as size and
mass, as well as identify possible atmospheres. Furthermore, the CHEOPS satellite
program will provide the possibility for an improved characterization also in terms of
habitability of exoplanets. The increasing number of newly detected planets raises issues
of possible other habitable worlds.
To investigate the atmospheric dynamics of habitable planets, we use a hierarchy of
general circulation models (GCMs). In a first step, we carry out these simulations using a
three-dimensional atmospheric GCM of intermediate complexity, the so-called Planet
For this study, sensitivity simulations varying different basic parameters of the planet are
performed to explore the range of habitability. Each simulation is carried out over 30 model
years. In doing so, we have modified gravity, radius, sidereal day, atmospheric
composition, distance to the star, and obliquity of the ecliptic. These simulations uses an
Earth-like environment (e.g., Earth land mask), which allows us to compare our
investigations with Earth observations. The range of surface temperatures determines the
habitability of a planet. Our simulations show, inter alia, that an increase in radius leads to
a reduction of the global mean temperature. We also find an impact on the amplitude of
the seasonality given by the gravity of the planet. The difference between maximum and
minimum temperature is enhanced with increasing gravity. Additionally, the variation of the
gravity changes the atmospheric structure: an increased gravity leads to a more stable
atmosphere above 700 hPa and to generally stronger wind fields and lower surface
temperatures on the planet. Furthermore, basic dynamical features such as the number of
jet streams will be assessed in the sensitivity simulations. The next steps also include a
model adaption with different land masks (e.g., aqua-planet).
A new perspective on the inner edge of the habitable zone: 3D modeling of runaway
greenhouse processes on Earth like planets
Jeremy Leconte — LMD (Paris) / CITA (Toronto)
Because current exoplanets detection methods are biased toward shorter-period orbits,
most planets discovered to date have a higher equilibrium temperature than the Earth. If
water is available at the surface, the amount of water vapor is expected to increase as the
planet warms, enhancing, in turn, the atmospheric greenhouse effect.
It has been shown that, above a certain critical insolation, this destabilizing greenhouse
feedback can "runaway" until all the oceans are evaporated. It has also been suggested
that warming may sufficiently increase stratospheric humidity to cause oceans to escape
to space before the runaway greenhouse occurs. However, the value of the critical
insolations triggering these processes remain uncertain because they have so far been
evaluated with unidimensional models that cannot account for dynamical effects and cloud
feedback that are key stabilizing features of planetary climates. Understanding and
modeling these processes is thus critical to accurately determine the extent of the
"Habitable Zone" around other stars.
We present results from a 3D global climate model specifically developed to describe hot,
extremely moist atmospheres to quantify Earth like planets climate response to an
increased insolation. In contrast with previous studies, we find that clouds have a
destabilizing feedback on the long term warming. However, subsident, unsaturated regions
created by the Hadley circulation have a stabilizing effect that is strong enough to defer the
runaway greenhouse limit to higher insolation than inferred from 1D models. Because of
these unsaturated regions, the stratosphere remains cold and dry enough to hamper
atmospheric water escape, even at large fluxes.
Finally, we will discus the implications of these results for Venus early water history and
the extent of the habitable zone around low mass stars when the rotation of the planet can
be tidally synchronized.
Terrestrial planet atmospheres in the aftermath of giant impacts!
Roxana Lupu — SETI Institute!
The final assembly of terrestrial planets is now universally thought to have occurred
through a series of giant impacts, such as Earth's own Moon-forming impact. After the
impact the surface of the surviving planet can remain hot for millions of years, making it
potentially detectable by direct imaging surveys. Here we explore the atmospheric
structures and spectral signatures of post-giant-impact terrestrial planets enveloped by
thick atmospheres derived from vaporized rock material. The atmospheric chemistry is
computed self-consistently for compositions reflecting either the bulk silicate Earth (BSE,
including the crust, mantle, atmosphere and oceans) or Earth's continental crust (CC). We
compute atmospheric profiles for surface temperatures ranging from 1000 to 2200 K,
surface pressures of 10 and 100 bar, and surface gravities of 10 and 30 m/s 2 . Our
calculations using extensive line lists bring a significant improvement over previous
models, but still do not include cloud formation and aerosol opacities. We find that the
post-giant-impact atmospheres are dominated by H2O and CO2, while the formation of
CH4, and NH3 is quenched due to short dynamical timescales. Other important
constituents are HF, HCl, NaCl, and SO2. Estimates including photochemistry and vertical
mixing show atmospheric enhancements in sulfur-bearing species, particularly SO2, which
produces strong spectral features. Estimated luminosities for post-impact planets, although
lower than predicted by previous models, show that the hottest post-giant-impact planets
will be detectable with the planned 30 m-class telescopes. Finally, we use the models to
describe the cooling of a post-impact terrestrial planet and briefly investigate its time
evolution. We find that the cooling timescale for post-giant impact Earths ranges between
10 5 and 10 6 years, where the slower cooling is associated with the planet going through a
runaway greenhouse stage.
The impact of stellar winds on exoplanetary magnetospheres
S.C. Marsden — University of Southern Queensland
The habitable zone of an exoplanet is traditionally defined by the range
of orbital distances where planetary surface temperatures are expected to
allow for liquid water. However, given that stellar winds can erode
planetary atmospheres even when a magnetosphere is present, it is proposed
that considerations of planetary habitability include stellar wind
pressure.The Bcool project is an international collaboration studying the
magnetic fields of solar-type stars and whose results can be used for
stellar wind studies. Using a simple wind model we show that an exoplanet
like the present-day Earth would generally need to orbit outside the
traditional habitable temperature zone of many solar-type stars to
maintain the size of its magnetosphere. However, planets orbiting within
the classical temperature habitable zone of solar-type stars should
possess magnetospheres that although compressed, are likely to protect the
planet's atmosphere and hence allow for the planet to be habitable.
An aqua planet under strong solar forcing!
Max Popp — Max Planck Institute for Meteorology
A modified version of the general circulation model ECHAM6 is used to investigate the
impact of increased total solar irradiance (TSI) on an aqua planet on a present-day Earthlike
orbit. We find that the present-day Earth-like climate destabilizes for a TSI between
1.06 and 1.08 times the present-day Earth value (S0). The aqua planet does not, however,
go into a Runaway Greenhouse, but attains a new steady state with global-mean seasurface
temperatures exceeding 335 K. This warm state is characterized by a low
meridional temperature gradient, a weak meridional circulation without polar cells, a moist
stratosphere and convection-dominated cloud formation. As the TSI is further increased,
the planet remains in the same regime of warm steady states for TSIs of at least up to 1.2
S0, because the cloud albedo increases as well, and balances the increased forcing. In
these states, the volume mixing ratio of water vapor in the upper atmosphere may attain
values as large as 0.015. This large mixing ratio exceeds the “Moist Greenhouse” limit
(Kasting et al. 1993) and suggests that a planet in such a warm state would hence be
subject to a rapid loss of water.
Climate dynamics of a coupled Aquaplanet
Josiane Salameh — Max Planck institute for Meteorology
The idea behind an Aquaplanet, an idealized configuration of the current Earth with all the
landmasses removed, is not recent. However, most of the research is conducted with
stand-alone atmospheric models. Thus, the originality behind considering the coupled
Aquaplanet setup, highlights the ocean's impact and allows us to directly interpret the
fundamental processes and feedbacks between ocean and atmosphere without any land
As for the few coupled Aquaplanet studies lately conducted on General Circulation
Models (GCM), they showed an extreme disparity regarding the final climate state. The
range of states discovered lies between a warm climate qualified with a lack of sea-ice
formation and a cold climate where sea-ice extend at the poles. Then, the existence of
three equilibrium states was verified while integrating the same GCM from different
random initial conditions.
The climate of a coupled Aquaplanet remains an open question. Therefore, our task is to
analyze the atmospheric-oceanic circulations of a coupled Aquaplanet while contributing to
this discrepancy in previous results. The simulations are executed on “ICON”, based on an
icosahedral triangular grid. Effects of rotation on Hadley cell's magnitude and extent, winds
distribution and others were already theoretically discussed and numerically tested. In
order to achieve a higher physical understanding of the Earth rotation rate and its effect on
the global circulation features, especially the ocean, our future goal is to consider variable
rotation rates in our coupled Aquaplanet setup.
The Effect of Host Star Spectral Energy Distribution on Planetary Climate
Aomawa Shields — University of Washington!
Planetary climate can be affected by the interaction of the host star spectral energy
distribution with the wavelength-dependent reflectivity of ice and snow. We have explored
this effect with a hierarchy of models. Results from both one-dimensional radiative transfer
and energy balance models and a three-dimensional general circulation model indicate
that terrestrial planets orbiting stars with higher near-UV radiation exhibit a stronger icealbedo
feedback. We found that ice extent is much greater on a planet orbiting an F-dwarf
star than on a planet orbiting a G- or M-dwarf star at an equivalent flux distance, assuming
fixed CO2 (present atmospheric level on Earth). The surface ice-albedo feedback effect
becomes less important at the outer edge of the habitable zone for main-sequence stars,
where the maintenance of surface liquid water requires high atmospheric CO2
concentrations. We show that 3-10 bar of CO2 will entirely mask the climatic effect of ice
and snow, leaving the outer limits of the habitable zone unaffected by the spectral
dependence of water ice and snow albedo. However, less CO2 is needed to maintain open
water for a planet orbiting an M-dwarf star than would be the case for hotter mainsequence
stars. We also explore the sensitivity of climate hysteresis to spectral energy
distribution, and examine how changes in planetary rotation rate and atmospheric
composition affect our results.
Marine Boundary Layer Clouds and their Interaction with the Large-scale
Atmospheric Circulation: An Idealized-GCM Study
Zhihong Tan! — California Institute of Technology / ETH Zurich
Cloud feedback is one of the central uncertainties in climate modeling, and the short-wave
radiative feedback of marine boundary layer (MBL) clouds is the most significant
contributor to these uncertainties. We have incorporated a physically motivated eddy
diffusivity/mass flux closure for convective turbulence coupled to a probabilistic cloud
scheme in an idealized aquaplanet GCM to develop improved turbulence and cloud
parameterizations and to study and constrain the physical mechanisms giving rise to cloud
feedbacks. Subtropical MBL clouds are observed in simulations with the idealized GCM.
We study their response to changes in the longwave optical depth and in the ocean heat
flux to determine the sign and magnitude of MBL cloud feedback over a wide range of
climates. We compare our results with previous modeling and observational studies, such
as the reported dependence of the MBL cloud fractions on the lower troposphere stability.
We discuss the mechanisms underlying the MBL cloud feedback and the degree to which
they can be expected to be robust, as well as the interaction of MBL processes with the
large-scale atmospheric circulation.
Climate and Photochemistry of Known Potentially Habitable Exoplanets
Feng Tian — Tsinghua University!
Several potentially habitable planets are known today. What are the environments like on
them Are they inhabited What are the potential signatures of life on them These are
important scientific questions for the coming decade(s). Photochemistry is important for
the climate on exoplanets by providing important species affecting radiation. On the other
hand, climate may pose important constraints on atmospheric composition, based on
which different schemes of photochemistry can perform. In this work we will discuss the
interplays between exoplanet climate and atmospheric composition and photochemistry,
focusing on potentially habitable exoplanets such as HD40307g and the GJ667C planets.
Water loss from terrestrial planets with N2/CO2 atmospheres!
Robin!Wordsworth! — University of Chicago!
The initial volatile content delivered to terrestrial planets during accretion is most likely
highly variable, with many planets receiving significantly more than Earth today possesses.
Understanding how later processes such as photolysis-driven H2O loss affect planetary
evolution is therefore vital to constraining the range of possibilities for both the early Solar
System and for many recently discovered low-mass exoplanets. Here we discuss a range
of calculations we have performed to study the dependence of water loss rates on a wide
range of planetary parameters. We show through a combination of simple analysis and
numerical climate models (1D and 3D) that the non-condensing atmospheric component
plays a fundamental role in controlling water loss via regulation of the stratospheric cold
trap. While CO2 can increase H2O transport to the high atmosphere over a small range of
mixing ratios by increasing surface temperature, thermodynamic constraints and cooling of
the middle/upper atmosphere act as a bottleneck on escape in other circumstances. The
differing relationships of total stellar luminosity and stellar XUV with time for G-stars places
strong limits on H2O loss rates for planets like Earth, although escape can reach higher
values for planets with surface liquid water around M-stars. Because the carbon cycles of
planets with ocean-covered surfaces are likely to be fundamentally different from that of
Earth, our results have important implications for the likely surface and atmospheric
characteristics of super-Earth exoplanets in the habitable zone.
Oceanic Circulation of Tidally Locked Terrestrial Planets!
Jun Yang — University of Chicago!
A fully coupled oceanic-atmospheric general circulation model is modified to simulate the
climate of tidally locked terrestrial planets. A central issue to be examined is to identify the
determining factors of oceanic circulation and its associated heat transport in both zonal
and meridional directions. In this study we will examine five planetary parameters: ocean
depth, land-sea distribution, rotational period (equaling to orbital period), planetary radius,
All these simulations show an eastward current along the equator, transporting heat from
dayside to nightside, and a meridional overturning circulation (MOC) in each hemisphere,
transporting heat from tropics to high latitudes. The equatorial current is driven by the
combined effect of surface wind streeses and Rossby waves in the ocean which transport
eastward momentum from high latitudes to the equator. The MOC is driven by salinity and/
or temperature contrasts between low and high latitudes. The salinity contrast results from
sea ice formation at high latitudes which releases salt to the ocean, and from sea ice
melting at low-latitude ice margins which decreases the salinity there. The strengths of the
oceanic circulation and heat transport are signifcantly influenced by the five planetary
parameters. We will further present how these parameters work.
Towards the Minimum Inner Edge Distance of the Habitable Zone
Andras Zsom — Massachusetts Institute of Technology!
We explore the minimum distance from a host star where an exoplanet could potentially be
habitable in order not to discard close-in rocky exoplanets for follow-up observations. We
find that the inner edge of the Habitable Zone for hot desert worlds can be as close as
0.38 AU around a solar-like star, if the greenhouse effect is reduced (low relative humidity),
and the surface albedo is increased.
We consider a wide range of atmospheric and planetary parameters such as surface
pressure, relative humidity, CO2 mixing ratio, surface gravity, etc. We argue that if the
dominant mode of precipitation is rain, the potentially habitable region is maximized on the
dry planet. Based on this argument, we estimate that relative humidity levels of 1% or
more can be sufficient to maintain a liquid water cycle. If the surface pressure is too low
(~0.1 bar), the water loss timescale of the planet is too short to support life. If the surface
pressure is too high (~100 bars), we show using atmospheric circulation arguments, that
the day-night side temperature difference on slow rotators is too small to enable an active
water cycle. Intermediate surface pressures (~1-10 bars) can provide suitable conditions
for a water cycle independent of the planetary rotation period. We additionally find that the
water loss timescale is influenced by the atmospheric CO2 level, because it indirectly
influences the stratospheric water mixing ratio.
We also show that the expected transmission spectra of hot desert worlds are similar to
an Earth-like planet. Therefore, an instrument designed to identify biosignature gases in an
Earth-like atmosphere can also identify similarly abundant gases in the atmospheres of dry
SUPER-EARTHS AND HOT NEPTUNES
The Atmospheres of GJ1214b and GJ436b: A Comprehensive Retrieval Study Based
on Unprecedented Data from Two Large-Scale HST Campaigns
Bjørn! Benneke — California Institute of Technology!
In this talk, we present the scientific interpretation for two unprecedented HST WFC3
campaigns to observe the transmission spectra of the warm exo-Neptune GJ436b and the
warm super-Earth GJ1214b. We report statistically robust constraints on the atmospheric
gas composition as well as the cloud properties such as cloud composition, cloud top
altitude, and particle size distribution.
Our main result for GJ1214b is that the observations require the presence of high-altitude
clouds at high significance, independent of the atmospheric composition and mean
molecular mass. We investigate the full range of physically plausible cloud properties that
may explain the observations. For GJ436b we find that high-altitude clouds could similarly
explain the observed flat transmission spectrum, suggesting that a similar cloud formation
mechanism may be at play in the two planets. Alternatively, we suggest the intriguing
possibility that GJ436b hosts an atmosphere which is strongly metal-enriched compared to
the gas and ice giants in our solar system.
The atmospheric constraints are obtained using a novel self-consistent inversion
framework that combines the observational data with our prior understanding of
atmospheric physics and chemistry in a statistically robust manner. The new framework
makes full use of all information at hand and identifies the full range of scenarios that are
both physically plausible and in agreement with the data. We describe the merits of this
new inversion framework for the interpretation of atmospheric spectra of both exoplanets
and Solar System planets.
How Do Mini-Neptunes Migrate
Zachory Berta-Thompson — Massachusetts Institute of Technology!
To understand an exoplanet, we need to know how it got where it is today. Because it
transits a very nearby, very small star, the exoplanet GJ1214b is a useful laboratory for
studying the physics of planets near the fuzzy boundary between super-Earths and sub-
Neptunes. However, little is known about how GJ1214b migrated to its current close-in
orbit. Was it scattered wildly inward and later tidally circularized, as many hot Jupiters
appear to have been Or was it coaxed in smoothly and gently, as seems to be the case
for the compact, coplanar, small-planet systems uncovered by Kepler To address this
conundrum, we search for and analyze recurrent starspot occultations in closely-spaced
transit light curves of GJ1214b taken with the Magellan, Gemini, and Hubble telescopes.
We use these spot occultations to constrain the relative orientation of the planet’s orbit to
the host star’s spin axis, which can be used to distinguish among possible scenarios for
the migration history of the planet. This analysis bears not only on the one particularly
useful GJ1214b system, but also on the processes that may shape many of the abundant
close-in, low-mass, low-density exoplanets that populate our Galaxy.
Water Cycling between Ocean and Mantle: Super-Earths need not be Waterworlds
Nicolas Cowan — Northwestern University
Large terrestrial planets are expected to have muted topography and deep oceans,
implying they should be entirely covered in water, so-called waterworlds. Quantitatively, a
planet ten times the mass of Earth is not expected to have exposed continents unless it
has a water mass fraction less than 3x10^-5, roughly ten times drier than Earth.
Waterworld climate is predicted to be less stable than that of planets with exposed
continents. Water is partitioned, however, between a surface reservoir, the ocean, and an
interior reservoir, the mantle. Plate tectonics transports water between these reservoirs on
geological timescales. Degassing of melt at mid-ocean ridges and serpentinization of
oceanic crust are mediated by sea-floor pressure, providing a stabilizing feedback on longterm
ocean volume. Motivated by Earth's approximately steady-state deep water cycle, we
develop a two-box model of the hydrosphere and derive steady-state solutions to the
water-partitioning on terrestrial planets. Since hydrostatic pressure is proportional to
gravity, super-Earths with a deep water cycle will tend to store most of their water in the
mantle. We conclude that tectonically active terrestrial planets with H2O mass fractions
less than 3x10 -3 will have both oceans and exposed continents.
Transiting planets around nearby M dwarfs: updates from the APACHE Project
Mario! Damasso — University of Padova
Across the Alps, just few hundreds km from Davos as the crow flies, a search for
transiting, small-size planets orbiting M dwarfs is in progress since July 2012: the APACHE
Project (A PAthway toward the Characterization of Habitable Earths). APACHE is a survey
“made in Italy” carried out as a collaboration between the Astronomical Observatory of the
Autonomous Region of Aosta Valley and INAF-Torino Astrophysical Observatory, which will
last five years and collect a huge database of photometric data. It uses five identical,
automatic 400mm telescopes to observe thousands of carefully selected nearby red
dwarfs. Nearby, bright M dwarfs are optimal targets as host stars for transiting planets
which can be extensively followed up to analyze their atmospheres, as demonstrated by
the case of the extrasolar planet GJ 1214b.
We present the results of the first observing season for several dozens of cool stars,
including detailed simulations aimed at estimating the sensitivity of APACHE to transiting
planets of different sizes. Moreover, we will discuss the results obtained for a sample of
stars which have been also monitored spectroscopically with HARPS-N@TNG in the
framework of the Large National Program GAPS.
In the spotlight: small planets transiting bright stars!
Diana!Dragomir — UC Santa Barbara/Las Cumbres Observatory Global Telescope
The Kepler transit survey has resulted in the discovery of more than a dozen super-Earth
planets. Super-Earths are of particular interest in exoplanet research because they
constitute a class of objects which are not represented in our Solar System, though
statistics from Kepler and radial velocity surveys suggest they are relatively common
around other stars. Moreover, these planets can theoretically have a wide range of
densities and therefore compositions which we have only very recently begun to explore
observationally. While studies of super-Earth hosting systems based on Kepler photometry
have contributed significantly to our understanding of these objects, follow-up observations
of these planets' atmospheres prove difficult or impossible to carry out with existing
instruments due to the faintness of most of the stars in the Kepler field. In order to better
understand the nature of this class of planets, we must focus on super-Earths transiting
bright stars (allowing for higher-precision observations) and/or small stars (leading to
deeper transits more amenable to transmission spectroscopy measurements). I will focus
on 55 Cnc e and HD 97658b, the two currently known transiting super-Earths which fall in
the former category. The 55 Cnc system has been observed with the MOST space
telescope for a total of 70 days over a period of three years. I will present results based on
the analysis of these data, including constraints on the secondary eclipse (and hence the
albedo) of 55 Cnc e, and discuss implications for the planet's atmospheric composition. I
will also present MOST photometry of HD 97658b and describe the current state of
knowledge of this low-density super-Earth's structure and composition, including a report
on our efforts to probe its atmosphere with the HST and Spitzer.
Atmospheric Composition of the ExoNeptune HAT-P-11b!
Jonathan D.! Fraine!— University of Maryland
We present new observations of the transiting exo-Neptune HAT-P-11b from a joint HST
and warm Spitzer program to measure the transmission spectrum of its thick atmosphere.
Our data cover a wide span of wavelength space, including warm Spitzer IRAC 3.6 & 4.5
micron photometry and Hubble WFC3 1.1 - 1.7 micron spectroscopy from our
observations, as well as Kepler's optical photometry centered at 632nm. Our WFC3
spectroscopic observations are among the first using HST's new spatial scanning mode for
optimised signal-to-noise spectroscopy. In addition, HAT-P-11 is one of the most active
planet-hosting stars; observations of HAT-P-11b's atmosphere therefore allow us to shed
light on the role that stellar activity may play in shaping the atmospheric chemistry of
Neptune-sized planets. We use the Kepler photometry to model and remove the effects of
the stellar activity during and surrounding our warm Spitzer transit observations. Our
combined observations provide constraints on the existence of clouds or hazes and the
atmospheric chemistry at the day-night terminator.
Neptunes in the Noise: Improved Precision in Exoplanet Transit Detection!
Aimée E. Hall — Institute of Astronomy, University of Cambridge!
SuperWASP is an established, highly successful ground-based survey that has already
discovered over 80 exoplanets around bright stars. It is only with wide-field surveys such
as this that we can find planets around the brightest stars, which are best suited for
advancing our knowledge of exoplanetary atmospheres. However, complex instrumental
systematics have so far limited SuperWASP to primarily finding hot Jupiters around stars
fainter than 10th magnitude. By quantifying and accounting for these systematics up front,
rather than in the post-processing stage, the photometric noise can be significantly
In this paper, we present our methods and discuss preliminary results from our reanalysis.
We show that the improved processing will enable us to find smaller planets
around even brighter stars than was previously possible in the SuperWASP data. Such
planets could prove invaluable to the community as they would potentially become ideal
targets for the studies of exoplanet atmospheres.
Water content and hydrogen-rich atmoshperes of sub-/super-Earths orbiting cool
Yasunori Hori — National Astronomical Observatory of Japan!
Over the past five years, close-in low-mass exoplanets orbiting cool stars has increased in
number rapidly. Recently, transmission spectra in a planetary atmosphere during a primary
eclipse have enabled us to explore the atmospheric compositions of super-Earths. Habitat
environment and formation histories of close-in planets are closely related to volatile
inventories in their atmospheres such as water and hydrogen. We have examined the
water content and the amount of hydrogen-rich atmospheres of sub-/super-Earths around
cool stars, performing 1,000 Monte Carlo simulations of planet formation. We have found
that super-Earths with 1-30 Earth-mass are likely to possess more than 20-30wt% water
mantles surrounded by thick H2-rich blankets: 0.1-20wt% H-He atmospheres for 1-10
Earth-mass planets inside 0.1AU, such as GJ 1214b, and more than 50wt% for larger
planets inside 1AU like GJ 436b. We have also shown that dry/wet sub-Earths with 0.1-1
Earth-mass inside 1AU end in naked ones with less than 1wt% H-He atmospheres. Our
results predict that sub-Earths in a habitable zone are wet but have almost no primitive
atmosphere, while super-Earths near/in the zone, for example, GJ 581d, GJ 667Cc, and
GJ 163c, contain abundant water and sufficient H2-rich atmospheres. Moderately-wet
planets with 0.001-1wt% water similar to the Earth, i.e., land planets, are either a small
fraction of sub-Earths near the inner edge or non-migrating planets near 1AU. In any case,
water worlds of sub-/super-Earths in a multiple-planet system are common around cool
Helium-Dominated Atmosphere on Neptune-Sized Exoplanet GJ 436b
Renyu Hu — California Institute of Technology!
The composition of the atmosphere on exoplanet GJ 436b, the most characterized
Neptune-sized exoplanet to date, has been a long-standing puzzle. The dayside emission
of the planet shows that its atmosphere is poor in methane and rich in carbon monoxide
and carbon dioxide, yet both equilibrium chemistry and disequilibrium chemistry models
predict most carbon to be in the form of methane for the temperature of the planet. This
contradiction is further intensified by the planet's large radius and low mean density, which
requires the planet to have an extensive gas envelope. Here we provide an explanation for
both the planet's emission spectrum and the planet\s radius. We propose that the
atmosphere of GJ 436b is mainly composed of helium. We have used a recently
established photochemistry-thermochemistry kinetic-transport model to compute the
molecular composition of the thick atmosphere on GJ 436b, with the helium versus
hydrogen ratio and the carbon and oxygen abundances as free parameters. The
temperature of the atmosphere is self-consistently computed using grey-atmosphere
approximation from the composition governed by disequilibrium chemistry. We find that a
helium-dominated atmosphere with hydrogen elemental abundance less than 3% by
number will have carbon dioxide and carbon monoxide as the main forms of carbon and
little methane, and thus lead to spectral features consistent with observations. Such an
atmosphere has mean molecular mass of ~4, only 2 times greater than that of a hydrogendominated
atmosphere, and therefore the helium-dominated atmosphere can be extended
enough to meet the mass-radius constraint of the planet. To form such a helium-dominated
atmosphere on a Neptune-sized exoplanet, we suggest that efficient hydrodynamic
atmospheric loss should have occurred in the early history of the planet. Hydrodynamic
escape has removed most of the hydrogen from gas accretion, and also removed some of
the helium, which resulted in the enrichment of helium in the planet's gas envelope. If this
mechanism is correct, one would expect helium-dominated atmospheres to be common on
Neptune and sub-Neptune sized exoplanets around M dwarfs.
Exploring the Relationship Between Exoplanet Mass and Atmospheric
Joshua Kammer — California Institute of Technology!
Studies of hydrogen-dominated planetary atmospheres in our solar system have shown
that as core mass fraction increases, so does atmospheric metallicity. This hypothesis
holds true for Uranus and Neptune, as these planets have atmospheres more enriched
relative to solar metallicity (30-40x) as compared to Jupiter (3x). Though these planets'
bulk densities are comparable to many detected exoplanets in the same size range, it
remains an open question whether the metallicities of exoplanet atmospheres also follow a
similar trend. One way to explore the correlation between planet mass and atmospheric
metallicity is by characterization of secondary eclipse emission spectra. For cooler
exoplanets (T < 1000 K) atmospheric models predict that carbon chemistry should be
dominated by CH4 rather than CO for an atmosphere of solar metallicity. Increasing the
atmospheric metallicity will suppress the amount of methane and enhance CO, as
proposed by Moses et al. (2013) to explain GJ 436b's unusually low methane-to-CO ratio.
Here we present results and analysis of Spitzer 3.6 and 4.5 μm secondary eclipse
observations of seven exoplanets with masses ranging from sub-Neptune to super-Jupiter
in size. Although they do not provide unique constraints on all the relative abundances of
water, methane, CO, and CO2, these measurements can reveal empirical trends in CH4-to-
CO ratios for cooler exoplanets in this size range, and test the correlation between
exoplanet mass and atmospheric metallicity.
Constraining the degeneracy of Super-Earth phase curve measurements
Daniel D.B. Koll — University of Chicago!
Thermal phase curve measurements of transiting exoplanets offer direct insight into how
efficiently their atmospheres redistribute heat. These measurements already indicate
distinct atmospheric circulation regimes on hot Jupiters, and stand to be a prime tool for
remotely characterizing Super-Earth atmospheres. However, for Super-Earths the
efficiency of atmospheric energy transport depends on a large number of difficult-toconstrain
parameters (atmospheric composition & mass, presence/absence of condensible
gases, surface type etc.). Assuming imperfect knowledge of these parameters, how
degenerate are phase curve measurements Can we use phase curve measurements to
robustly distinguish between different atmospheric scenarios, or do we need additional
information from, e.g., transit spectroscopy
To answer this question, it is necessary to comprehensively map out how the
atmospheric energy transport depends on a large number of atmospheric parameters. To
make the problem computationally tractable we non-dimensionalize the primitive equations
and equations of grey-gas radiative transfer and find a reduced set of non-dimensional
numbers that govern the atmospheric dynamics. We present simulations with an idealized
dry global climate model (GCM) to demonstrate the utility of this approach. We also
present results on how the atmospheric energy transport varies over the phase space
spanned by these non-dimensional numbers, focusing on the relative roles of dynamics,
radiation and uncertain model parameterizations.
Transmission Spectroscopy of the Super-Earth Archetype GJ 1214b!
Laura! Kreidberg — University of Chicago!
Super-Earths, exoplanets intermediate in size between Earth and Neptune, are among the
most prevalent planets in the Galaxy. Revealing the composition and formation histories
of these common objects requires atmospheric characterization. I will present the results
of an intensive observational campaign to study the atmosphere of the super-Earth
archetype GJ 1214b. We observed 15 transits of the planet with the Hubble Space
Telescope in the near-infrared, yielding the most precise exoplanet transmission spectrum
measurement ever obtained in this wavelength range. Our measurements definitively
distinguish between clear, high mean molecular weight atmospheric models and models
with high-altitude clouds. I will also discuss preliminary results of a Gemini program to
measure the transmission spectrum in the blue optical.
Understanding Kepler's Super-Earths and Sub-Neptunes: Insights from Thermal
Evolution and Photo-Evaporation!
Eric Lopez — UC Santa Cruz
NASA's Kepler mission has discovered a large new population of super-Earth and sub-
Neptune sized planets. Although we have no analogous planet in our own solar system,
such planets are incredibly common. Understanding the nature and formation of systems
of these planets is one of the key challenges for theories of planet formation. We use
models of thermal evolution and photo-evaporation to constrain the structure, composition,
and evolution of low-mass planets. Over time Neptune-like planets with large H/He
envelopes can be transformed into rocky super-Earths. We show that differences in mass
loss history provide a natural explanation for many features of the Kepler multi-planet
systems, such as large density contrast between Kepler-36b and Kepler-36c. For the
oader population of Kepler planets, we find that there is a threshold in bulk planet
density, mass, and incident flux above which no low-mass transiting planets have been
observed. We suggest that this threshold is due to XUV-driven photo-evaporation and
show that it is well reproduced by our evolution models.
Chemical Characterization of Super-Earths: Interiors, Atmospheres, and Formation
Nikku! Madhusudhan — Yale University
Recent advances in exoplanetary science are leading to unprecedented observations of
super-Earths. The observed masses, radii, and temperatures of super-Earths provide
constraints on their interior structures, geophysical conditions, as well as their atmospheric
compositions. Some of the most recently detected super-Earths span a wide gamut of
possible compositions, from super-Mercuries and lava planets to water worlds with thick
volatile envelopes. In this work, we report joint constraints on the interior and atmospheric
compositions of several super-Earths and discuss their possible formation scenarios using
new and comprehensive hybrid models of their interiors, non-gray atmospheres, and
formation conditions. Our model constraints are based on the masses and visible radii, as
well as the latest infrared measurements of transmission and emission spectrophotometry
where available, in addition to revised estimates of the stellar parameters. We will present
a comparative analysis of several transiting super-Earths currently known and will discuss
in detail two super-Earths (GJ 1214b and 55 Cancri e) which have atmospheric data
available and which represent two distinct end members in the thermo-chemical phase
space of super-Earth conditions. We will also discuss the implications of our results for the
diversity of geochemical and geophysical conditions on super-Earths. We will conclude
with comments on new observational, theoretical, and experimental efforts that are critical
to detailed characterization of super-Earths.
Multi-Color Simultaneous Transit Photometry of Planets around Cool Host Stars
Norio Narita — National Astronomical Observatory of Japan
Transmission spectroscopy is a powerful method to investigate planetary atmospheres for
transiting exoplanets. For ground-based large (6-10 m class) telescopes, multi-object
spectroscopy and high dispersion spectroscopy have shown successful results for this
purpose. For smaller (1-2 m class) telescopes, multi-color simultaneous transit photometry
provides an alternative and efficient way for transmission spectroscopy. In this talk, we
focus on such multi-color simultaneous transit photometry for planets around cool host
stars, including GJ1214, GJ3470, and WASP-80. We present some observational results
taken in 2011 and 2012 seasons (e.g., Narita et al. 2013a, Narita et al. 2013b, Fukui et al.
2013) and preliminary results for data taken in 2013 season.
Characterizing the Demographics of Exoplanet Bulk Compositions
Leslie Rogers — California Institute of Technology
The Kepler Mission has discovered thousands of sub-Saturn-sized transiting planet
candidates. Using planet interior structure models, we constrain the bulk compositions of
the more than 50 known sub-Saturn-sized transiting planets with measured masses. Our
model considers fully differentiated planets comprised of up to four layers: an iron core, a
silicate mantle, a water mantle, and a gas envelope. We calculate the planet interior
structure by integrating the coupled differential equations describing an evolving selfgravitating
body, employing modern equations of state for the iron, silicates, water, and
gas. For any individual planet, a wide range of compositions is consistent with the
measured mass and radius. We consider the planets as an ensemble, and discuss how
thermal evolution, mass loss, and observational biases sculpt the observed planet massradius-insolation
distribution. Understanding these effects is crucial for constraining the
demographics of small planet bulk compositions and for extracting signatures of the planet
formation process from the accumulating census of transiting planets with dynamical
Ground-based search for the transit of Alpha Cen Bb
Aurelien Wyttenbach — Geneva Observatory
In late 2012, a planet with a minimum mass of 1.13 earth mass may have been detected
around Alpha Cen B with the HARPS spectrograph. With a 3.2 days orbit, the planet has a
10% transit probability. However, with an expected transit depth of ~100 ppm, searching
for the transit is challenging, especially from the ground because of correlated noise in the
light curves. The extreme brightness of Alpha Cen B, and the close separation from Alpha
Cen A (4") complicate the task further. We have developed and tested a method designed
to beat down correlated noise, while coping with the brightness and duplicity of the Alpha
Cen system, using high-resolution spectroscopy. Here, we present the first light curve of
Alpha Cen B obtained using this method during one night of observations with UVES at
HOT JUPITERS: OBSERVATIONS
Spectrophotometry with SOFIA: First results!
Daniel!Angerhausen — Rensselaer Polytechnic Institute
Over the past decade the transit method (measuring the small, wavelength-dependent
variation in flux as an exoplanet passes in front of or behind its parent star) has produced
a number of exciting characterization results. The NASA/DLR Stratospheric Observatory
for Infrared Astronomy (SOFIA), a 2.5-meter infrared telescope on board a Boeing 747-SP,
has a specific and unique phase space for these extremely precise time-domain
spectrophotometric observations at IR wavelengths: It operates in the right wavelength
regime, where the planet's black-body temperature peaks and contrast ratios between star
and planet improve. The airborne observatory is able to avoid most of the perturbing
variation of atmospheric trace gases that produce the dominant source of noise for
ground-based observations in the near-infrared. These telluric molecules are also the
species of interest in the exo-atmospheres. The SOFIA telescope is operating at much
lower temperatures (~240 K) than ground-based telescopes (~273 K). Therefore thermal
background contributions, the dominant noise source for transit observations at
wavelengths longer than 3 micron, will be significantly reduced. The mobile platform
SOFIA can observe time-critical events, such as the rare transits of long-period planets,
under optimized conditions. After the end of Spitzer and until the start of the JWST
mission, SOFIA will be the only observatory capable of NIR spectrophotometry of
exoplanet atmospheres beyond 1.7 micron (the upper limit for HST after the last upgrade)
at an altitude where the impact of variable telluric absorption is small enough for high
precision observations of the same molecules also present in exoplanet atmospheres.
Here we present SOFIA's unique advantages in comparison to ground- and space-based
observatories in this field of research and present the very first spectrophotometric
exoplanet observations that were or will be conducted in SOFIA’s cycles 1 and 2.
Characterisation of Exoplanets using Polarization!
Jeremy Bailey — University of New South Wales!
Light reflected from the atmospheres of extrasolar planets will be polarized, and the
detection and measurement of that polarization provides a means of characterising the
atmospheres that provides complementary information to that from spectroscopy. At
UNSW we are building a new instrument with the aim of measuring polarization in the
combined light of a star and hot Jupiter planet, and thus detecting the polarization of the
planet. We have also incorporated polarization capability into our atmospheric modelling
code VSTAR. Polarization is particularly sensitive to the presence of atmospheric clouds
and hazes. I will describe our current progress on these developments, and discuss the
potential of such techniques for the study of exoplanet atmospheres.
Polarimetric detection and characterization of hot Jupiters!
Andrei! Berdyugin — FINCA, University of Turku, Finland
The light scattered in planetary atmospheres is linearly polarized perpendicular to the
scattering plane. In general, when the planet rotates around the parent star, the scattering
angle changes and the Stokes parameters Q and U of linear polarization vary. If the orbit is
close to circular, two peaks per orbital period are observed. The observed polarization
variability exhibits therefore the orbital period of the planet and reveals the inclination,
eccentricity, and orientation of the orbit. Due to proximity to the star, hot giant planets with
short orbital periods ("hot Jupiters") may develop extended peculiar atmospheres and
halos which effectively scatter the light in the blue spectral region. This can give rise to a
degree of polarization detectable with the currently existing modern polarimeters.
Parameters of this polarization, e.g., wavelength dependence, are defined by physical
conditions in the upper layers of the planetary atmosphere. Thus, polarimetry of hot "blue
Jupiters" in combination with other methods of observations may be used to draw
conclusions on properties of their atmospheres.
Here we present new polarimetric observations of several hot Jupiters, both transiting
and non-transiting, in three bands: blue, green, and red. These data were obtained with
two instruments: (1) our new Double Imaging Polarimeter (DIPol-2) at the 60cm KVA
telescope on La Palma, routinely providing polarimetric accuracy of 10 -5 , and (2) the FORS
polarimeter at the VLT, ESO, with the maximum accuracy of 10 -4 . We analyze these data
using our model calculations and infer planet orbit parameters and atmosphere reflectivity.
We compare our results with measurements of the secondary eclipses of hot Jupiters.
Detecting water in hot Jupiter atmospheres with high-resolution ground-based
Jayne!Birkby — Leiden Observatory
The robust determination of the chemical make-up of exoplanet atmospheres is crucial to
understanding their structure, formation, and evolution, particularly in the case of the major
carbon- and oxygen-bearing species. We present ground-based high-resolution spectra
from CRIRES/VLT at 3.2 microns of several transiting and non-transiting hot Jupiter
atmospheres (51 Peg b, Tau Boo b, and HD 209458 b), in which we have searched for the
radial velocity signature of water, methane and carbon dioxide molecules in the planetary
atmospheres. We compare the results of our search with the detections of CO already
reported in these hot Jupiter atmospheres, and discuss their temperature-pressure profiles
and relative abundance ratios. Preliminary results indicate a significant abundance of
water in 51 Peg b, consistent with tentative reports of water at 2.3 microns.
Observation of Magnesium : A new Probe of Exoplanets' Thermospheres and
Vincent Bourrier — Institut d'Astrophysique de Paris
Transit observations of HD209458b in the UV revealed signatures of neutral magnesium
escaping the planet upper atmosphere. The absorption detected in the MgI line arises from
the transition region between the thermosphere and the exosphere, and provides
unprecedented information on the physical conditions at the altitude where atmospheric
escape takes place. These observations have been interpreted using a 3D particle model
coupled with an analytical modeling of the atmosphere below the exobase. Thus we
estimated the planetary wind velocity and the exobase altitude, and also obtained an new
estimate of the atmospheric escape rate. More generally, we show that magnesium
absorption lines provide a powerful tool to study the upper part of exoplanets'
atmospheres. We identified a dozen of exoplanets with host stars bright enough for their
atmosphere to be observed using the magnesium lines.
Probing the atmospheres of non-transiting exoplanets: CO and H2O absorbtion in
Matteo Brogi! — Leiden Observatory
In recent years, ground-based high-resolution spectroscopy has become a powerful
method for studying exoplanet atmospheres. It is capable to robustly identify molecular
species via line matching, and to detect the radial velocity of the planet itself. Moreover, by
targeting the planet thermal emission directly, it does not require the planet to transit.
Thanks to this method, the mass and orbital inclination of non-transiting planets can be
determined and their atmospheric composition studied.
I will present our latest K-band observations of HD179949b with CRIRES at R=100,000.
We detect an absorption signal from water vapour and carbon monoxide at SNR=6.5,
meaning that the portion of the planet’s atmosphere probed by these observations does
not have an inversion layer. The derived mass and orbital inclination for the planet are
(0.98+/-0.04) Jupiter masses and (68+/-4) degrees respectively.
Except for young, self-luminous directly-imaged planets, only high-resolution
spectroscopy currently allows the atmospheric characterization of non transiting planets.
With the next generation of ELTs and this technique, a complete census of this class of
bodies will be possible, revealing for the first time their properties and actual mass
Spectroscopic observations of the hot-Jupiter HD 189733b with HST WFC3
Nicolas Crouzet — Space Telescope Science Institute
Spectroscopic observations of exoplanets are crucial to infer the composition and
properties of their atmosphere. In particular, identifying molecular features and measuring
their amplitude constrain the presence of and the effect of clouds, which are thought to
play a major role in the atmosphere of hot-Jupiters. After a controversy on the reliability of
NICMOS results, the Wide Field Camera 3 (WFC3) on board the Hubble Space Telescope
now delivers hot-Jupiter spectra with much higher fidelity than HST NICMOS had in the
past. We observed the well studied hot-Jupiter HD 189733b with WFC3 in the bandpass
1.1 to 1.7 microns using the newly implemented spatial scanning mode, which largely
increases the number of collected photons compared to the staring mode. Also, the
spatially-scanned WFC3 data produce satisfactory results with a very straight-forward
analysis, a welcome change from the old technique of staring-mode observations,
especially those obtained with HST NICMOS (Crouzet et al. 2012). We will discuss the
amplitude of absorption seen in the transmission spectrum and the inferred atmospheric
composition for HD 189733b, and compare them with recent results by Deming et al.
(2013) for the exoplanets HD 209458b and XO-1b using similar WFC3 data. Our data
reinforces the idea that molecular features of hot Jupiters may be attenuated by the
presence of clouds or haze. We derive the planetary emission spectrum using the same
technique with observations made at secondary eclipse.
A Closer Look at Correlated-Noise Measuring Techniques for Exoplanet Light
Patricio Cubillos — University of Central Florida
Among the many exoplanet light-curve fits analyzed to date, it is not unusual to detect
some degree of time correlation in the residuals (also known as correlated or red noise).
An incorrect assessment of correlated noise can lead to under- or overestimating the
uncertainties on the planet's physical parameters, giving more or less significance to the
results than they should have. While the sources of correlated noise are not always
known (e.g., from an inaccurate systematics treatment or some unaccounted astrophysical
effect), there are methods that aim to assess the degree of correlated noise, like the RMSvs.-bin
size plot, prayer beads, and wavelet-based likelihood fitting. Yet, there are no indepth
statistical studies in the literature for some of the techniques currently used.
We subjected these correlated-noise assessment techniques to basic tests on synthetic
data sets to characterize their features and limitations.
Initial results indicate, for example, that sometimes the RMS-vs.-bin size plot has large
artifacts when the bin size is similar to the observation duration. Further, prayer beads
rarely indicate the right level of correction for correlated noise. We have applied these
techniques to several Spitzer secondary-eclipse hot-Jupiter light curves and discuss their
New possibilities for exoplanet observations at high spectral resolution
Remco de Kok — SRON
In the last few years there have been several detections of molecules in hot-Jupiter
atmospheres using observations at very high spectral resolution (R=100,000), most
notably using CRIRES on the VLT. These observations have the great advantage that they
allow unambiguous detection of specific molecules. On the other hand, determining
abundances of molecules in the atmosphere has not yet been possible using only highresolution
observation due to degeneracies. We will discuss what other high-resolution
measurements can be performed with current instruments to obtain a better understanding
of the chemistry and dynamics of hot-Jupiter atmospheres. We will present results from
our sensitivity analysis of simulated CRIRES observations, showing at what wavelengths
particular molecules are best detected. We will also discuss whether molecules can be
detected from high-resolution thermal radiation from the night-side. We find that for some
planets the night-side might even yield a larger signal than the day-side.
2D mapping of the eccentric exoplanet HAT-P-2b!
Julien!de Wit — Massachusetts Institute of Technology
The class of close-in gas giant planets known as hot Jupiters provides an exceptional
insight into atmospheric circulation, as these planets are expected to be both highly
irradiated and in either synchronous or pseudo-synchronous orbits depending on their
orbital eccentricity. We can probe atmospheric circulation through phase curve
measurements, which tell us about their brightness as a function of longitude. Recently, a
new observational tool, “eclipse mapping”, has been developed enabling the creation of
maps that are resolved in both longitude and latitude, unlike phase curves. To date, only
one planet (HD 189733b) has been successfully mapped using this technique. Here, we
present the first two-dimensional maps of the eccentric exoplanet HAT-P-2b in the Spitzer
4.5 micron bandpass. This map is derived from fourteen new secondary eclipses observed
in the 4.5 micron band.
The high eccentricity of HAT-P-2b leads to fundamental differences between its
atmospheric circulation and that of HD189733b. A high eccentricity prevents tidal locking
and implies time-variable stellar heating, hence time-variable forcing. HAT-P-2b is eclipsed
post-periastron, hence we use eclipse mapping to gain insights into how its atmosphere
responds to transient heating. In particular, HAT-P- 2b’s map will yield constraints on its
radiative and advective time-scales and probe the spatial extent of its dayside thermal
inversion. We will discuss the implication of our findings in the context of atmospheric
circulation models that can be applied to a wide range of planets.
Mapping Clouds in Exoplanet Atmospheres
Brice-Olivier Demory — Massachusetts Institute of Technology
Clouds and hazes are ubiquitous in the solar system's giant planet and brown-dwarf
atmospheres. It has been long suggested that clouds would also play a strong role in
shaping the spectra of exoplanets in general and hot Jupiters in particular. Recently,
clouds have been reported in the atmosphere of HD189733b. We will present the first
results of a program aiming at detecting and characterizing clouds in hot-Jupiter
atmospheres. We use joint space-based visible+IR occultation and phase-curve
photometry to reconstruct low-resolution maps of thick clouds. We will discuss the possible
formation scenarios for these clouds and explore the degeneracies involved in the retrieval
of the particles properties (coverage, size distribution, vertical extent, composition, shape,
etc.). We will finally discuss how near-to-come space- and ground-based facilities will
contribute to the detailed characterization of these clouds.
Characterising Exoplanets Using Kepler Phase-Curves!
Lisa Esteves — University of Toronto!
Although the Kepler mission is mainly aimed at searching for exoplanet transits, its highprecision
photometry and long-term monitoring of the same field, makes it ideal to use for
phase-curve measurements. Recently, using almost four years of Kepler data, we have
been able to measure the phase-curve of eight Kepler objects. For five of these we
present the very first phase-curve measurements, while for the other three objects we
present greatly refined parameters. In addition we demonstrate how phase-curves
measurements can be used as a very powerful tool for ruling out false positives within the
Kepler planet candidate population.
Measuring the reflection signal of HD189733b!
Tom Evans — Oxford University!
The multi-wavelength reflection signal of an exoplanet provides a valuable insight into the
composition and structure of its atmosphere. In this talk, I will describe our measurement
of a secondary eclipse of HD189733b across the 290-570nm wavelength range, made
using HST/STIS. We found that the albedo of the planet decreases towards longer
wavelengths in this range from approximately Ag=0.4 to Ag
data reduction stage crucial to our current understanding of exoplanet atmospheres. This
has prompted the development of new, sophisticated techniques to robustly extract signals
from transit data, and also a drive to use new observing facilities to re-observe and confirm
exoplanet signals. Ground-based telescopes are now playing an increasingly prominent
role, with multi-object spectrographs enabling differential ground-based spectrophotometry.
These observations are now providing similar precision to space-based observations
where appropriate comparison stars are available, and should allow us to verify spacebased
spectra and ease our dependence on single instruments. Here, we present efforts
to measure transmission spectra using the Gemini telescopes, with the GMOS multi-object
spectrographs, and discuss how we extract the atmospheric signals in the presence of
complex noise sources. We report transit observations of WASP-29, HAT-P-32 and
(possibly) HAT-P-33, reaching sufficient precision to probe atmospheric features. These
reveal featureless spectra possibly caused by the presence of clouds in the upper
atmospheres, although further observations are required to confirm this.
On the Statistical Significance of Trends in Exoplanetary Emissions!
Joseph Harrington — University of Central Florida
We have examined the fluxes of exoplanetary atmospheres as measured during
secondary eclipses. Cowan and Agol (2011) and we (Harrington et al. 2007, 2010, 2011,
2012, 2013) have noted that at equilibrium temperatures above about 2000 K (zero
albedo, uniform redistribution), observed exoplanet fluxes are substantially higher than
even the elevated equilibrium temperature predicts. With a substantial increase in the
number of atmospheric flux measurements, we can now test the statistical significance of
this trend. We can also cast the data on a variety of axes to search further for the physics
behind both the jump in flux above about 2000 K and the wide scatter in fluxes at all
Enshrouded Close-In Exoplanets
Carole Haswell — Open University
Our near-UV HST observations of the extreme hot Jupiter WASP-12b revealed
extended exospheric gas overfilling the planet\s Roche lobe and causing
reproducible enhanced transit depths at 65 distinct wavelengths. There is
complete absorption, i.e. zero emergent flux, in the cores of the very strong
MgII h&k lines at all observed orbital phases.
I will present several lines of evidence to show this is due to diffuse gas lost
from WASP-12b, which enshrouds the entire planetary system. Our results suggest a new
interpretation of the known correlation between hot Jupiter atmosphere type and host star
activity as indicated by the cores of the very strong CaII H&K lines. I will present recent
observations of the putative evaporating rocky exoplanet KIC 1255b. WHT/ULTRACAM
simultaneous multiwavelength light curves obtained in July 2013 have implications for the
dust scattering function,an empirical upper limit on the size of the planet, and the limitcycle
mechanism which modulates the observed dust extinction. We used CFHT/
ESPaDOnS to perform transmission spectroscopy searching for metal rich vapour
expected to co-exist with the dust as the gas phase component of the planetary mass loss.
Finally I will discuss the general implications of these findings for the Galaxy’s population
of planets and for studies of star-planet interactions.
Characterization of Exoplanets using Planetary Radial Velocimetry!
Hajime Kawahara — The University of Tokyo!
Recently radial velocity curves of exoplanets have been measured with the aid of the high
dispersion instrument CRIRES on VLT (e.g. Snellen et al. 2010, Brogi et al. 2012, Rodleret
al. 2012, Birkby et al. 2013). I consider the effect of planet’s spin on the planetary radial
velocity. With simple assumptions, I find that the radial velocity curve is distorted by the
planetary spin and this anomaly is characterized by spin radial velocity at equator and a
projected angle on a celestial plane between the spin axis and the axis of orbital motion
(Kawahara 2012). I will discuss the feasibility of the precise planetary radial velocity
measurement for such as the spin measurement, with possible instruments in near future.
Polarimetry of transiting exoplanetary systems!
Nadiia!Kostogryz — Kiepenheuer-Institut für Sonnenphysik!
Since the discovery of the first extrasolar planet, methods of their detection and
characterization are rapidly developing. The best-characterized planets are so far those
which were detected by different methods. Thanks to the recent high-accuracy polarimetric
instruments, polarimetry has become an independent technique for characterizing
exoplanetary systems as it yields information inaccessible to other methods. As was
shown observed polarization variability due to scattering in the planetary atmosphere
reveals the orbital period of the planet, inclination, eccentricity, orientation of the orbit as
well as the nature of scattering particles in the planetary atmosphere.
We present and discuss another polarimetric effect caused by a planet transiting the stellar
disk and, therefore, breaking its symmetry and resulting in linear polarization of a partially
eclipsed star. Such an effect was predicted in 1950 for binary stars, and it was first
detected in the eclipsing binary Algol. Estimates of this effect for transiting planets were
made only recently. In particular, we demonstrated that the maximum polarization for one
of the brightest transiting planets HD189733b strongly depends on the centre-to-limb
variation of linear polarization for the host star. However, observational and theoretical
studies of the limb polarization have been largely concentrated on the Sun. As was shown
in our previous study, we expect to observe a larger centre-to-limb linear polarization for
cooler stars. Here we solve the radiative transfer problem for polarized light and simulate
the centre-to-limb polarization for stars of different spectral classes taking into account
various opacities. Knowing stellar limb polarization is also necessary for evaluating stellar
contribution when interpreting scattering polarization from spatially unresolved planets at
elongations. In addition, the radius of the grazing planet can be determined from transit
polarimetry when transit photometric data become unreliable. Employing our simulations
for all transiting exoplanets we select most promising targets for future polarimetric
Detecting Exoplanetary Magnetic Fields
Joe Llama — University of St Andrews
In this work we explore the possibility of detecting magnetic fields around extrasolar
planets using asymmetries in their transit light curves. Observations of the very close-in,
highly inflated planet WASP-12b have revealed an asymmetry in the near-UV light curve
when compared to the optical transit. It has been suggested that this asymmetry may be
caused by the stellar wind colliding with the magnetosphere of the planet, resulting in the
formation of a magnetospheric bow shock. We show how modelling such a shock allows
us to reproduce this transit asymmetry and to place constraints on the magnetic field
strength of the planet.
Characterizing Exoplanet Atmospheres with HST/WFC3
Avi Mandell — NASA GSFC !
The Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) provides the
potential for spectroscopic characterization of molecular features in exoplanet
atmospheres, a capability that has not existed in space since the demise of NICMOS on
HST and the IRS on Spitzer. We present an analysis of transit spectroscopy for three
extrasolar planets observed during the HST Cycle 18: WASP-12 b, WASP-17 b, and
WASP-19 b. WASP-12 b and WASP-19 b are two of the hottest exoplanets discovered to
date, while WASP-17 b has a much lower equilibrium temperature but has one of the
largest atmospheric radii of known transiting planets; measurement of molecular
absorption in the atmospheres of these planets offers the chance to explore several
outstanding questions regarding the atmospheric structure and composition of these highly
irradiated, Jupiter-mass objects. The observations cover a single primary transit for each
planet, and we analyze the data using a strategy that allows us to correct for channel- or
wavelength-dependent instrumental effects by utilizing the band-integrated time series and
measurements of the drift of the spectrum on the detector over time. We achieve almost
photon-limited results for individual spectral bins, but the uncertainties in the transit depth
for the the band-integrated data are exacerbated by the uneven sampling of the light curve
imposed by the orbital phasing of HST observations. Our final transit spectra for all three
objects are consistent with the presence of a broad absorption feature at 1.4 microns most
likely due to water. However, the amplitude of the absorption is less than that expected
based on previous observations with Spitzer, possibly due to hazes absorbing in the NIR
or non-solar compositions. The degeneracy of models with different compositions and
temperature structures combined with the low amplitude of any features in the data
preclude our ability to place unambiguous constraints on the atmospheric composition, but
future observations with WFC3 to improve the S/N and/or a comprehensive multiwavelength
analysis will allow us to better distinguish between different models.
HST/STIS Transmission Spectral Survey: Probing the Atmospheres of HAT-P-1b and
Nikolay Nikolov — University of Exeter
We present optical to near-infrared transmission spectra of HAT-P-1b and WASP-6b, part
of a Large HST/STIS hot Jupiter transmission spectral survey (P.I. David Sing). The
spectra for each target cover the regimes 290-570nm and 524-1027nm, with resolving
power of R = 500. The HAT-P-1b data is coupled with a recent HST/WFC3 transit,
spanning the wavelength range 1.087-1.687 micron (R=130), acquired in spatial scan
mode. The WASP-6b data is complemented with Spritzer/IRAC 3.6 and 4.5 micron transit
observations, part of a comparative exoplanetology program (P.I. Jean-Michel Desert). The
transmission spectrum of HAT-P-1b shows a strong absorption signature shortward of
550nm, with a strong blueward slope into the near-UV. We detect atmospheric sodium
absorption at a 3.3-sigma significance level, but see no evidence for the potassium
feature. The red data implies a marginally flat spectrum with a tentative absorption
enhancement at wavelength longer than ~850nm. The combined STIS and WFC3 optical
to NIR spectra differ significantly in absolute radius level (4.3+/-1.6 pressure scale
heights), implying strong optical absorption in the atmosphere of HAT-P-1b. The optical to
near-infrared difference cannot be explained by stellar activity, as simultaneous stellar
activity monitoring of the G0V HAT-P-1b host star and its identical companion show no
significant activity that could explain the result. The red transmission spectrum of
WASP-6b is flat with tentative detection of sodium and potassium. We compare both
spectra with theoretical atmospheric models which include haze, sodium and an extra
optical absorber in the case of HAT-P-1b. We find that both an optical absorber and a
super-solar sodium to water abundance ratio might be a scenario explaining the HAT-P-1b
Characterizing Hot Jupiter Atmospheres with Ground-Based Facilities: Instrument
Performance and New Results
Lisa Nortmann — University of Göttingen
Transiting planets are of particular interest for exoplanet atmosphere science as the
geometry of their orbits enables us to investigate atmospheric transmission spectra.
During transit the upper layers of an exoplanet atmosphere are penetrated by its host
star’s light. As a consequence the fingerprint of the atmospheric composition at the
terminator region can be observed in form of a color dependent variation in the occultation
depth. One of the biggest remaining challenges of multi-color transit observations is the
proper removal of systematic noise signals. Such signals are frequently found to distort the
light curves in data of both ground-based and space-based origin and in many cases their
source is not well understood.
Our group uses the ground-based facilities ESO/VLT+FORS2 and the Spanish 10-meter
telescope GranTeCan+OSIRIS to probe the atmosphere of hot Jupiters with the technique
of multi-object spectrophotometry. I will address our new findings regarding the source and
nature of instrument specific systematics that we noticed to commonly affect data taken
with these two instruments. Furthermore, I will introduce our approach to the correction of
these noise signals, which allows us to retrieve high quality spectrophotometric data. As an
example I will present the transmission spectra of the two hot Jupiters WASP-17b and
HAT-P-32b which we obtained in the optical wavelength region between 500 and 1000 nm.
In this broad wavelength interval the transmission spectra of hot Jupiters are predicted to
exhibit sodium, potassium, water and titanium/vanadium oxide absorption. The abundance
of these atmospheric species is of particular interest, as they serve as good indicators for
the prevalent temperature and, consequently, can help to shed light on the mechanisms of
heat re-distribution between the planet’s day and night side.
A Secondary Eclipse Survey of the Hottest Exoplanets with Palomar and Spitzer!
Joseph G. O'Rourke — California Institute of Technology
Combined ground- and space-based secondary eclipse observations provide an
invaluable window on the dayside emission spectra for transiting exoplanets, as
demonstrated by recent studies of WASP-12b. Here, we present preliminary results from
our survey of hot Jupiters with relatively high temperatures (>2000 K). We utilize
secondary eclipse photometry at 3.6 and 4.5 µm taken with the IRAC camera aboard the
Spitzer Space Telescope during the warm Spitzer mission and in the H and Ks bands with
the WIRC camera at the Palomar 200-inch Hale Telescope. We discuss how the
installation of a new diffusing filter in the WIRC filter wheel mitigates many of the
systematic problems encountered during ground-based observations. With multiwavelength
photometry and spectroscopy for a large sample of hot Jupiters, we can
search for trends in atmospheric characteristics, including elemental abundances, C/O
atios, and temperature profiles, that might be important clues to their formation and
Models of exoplanet evaporation
James! Owen — Canadian Institute for Theoretical Astrophysics
Given the numerous exoplanets discovered at close separations to their parents stars,
where the stellar UV & X-ray radiation fields can heat the upper layers of the planets
atmosphere to 10 4 K, evaporation is bound to occur. I will discuss evaporation in the
hydrodynamic limit which can be driven by either the EUV or X-ray radiation, and the
associated mass-loss rates. I will argue that evaporation of close-in exoplanets does not
occur in `energy-limited' sense where PdV work dominates the energy loss, but that
radiative cooling and recombinations are dominant energy sinks. Finally, I will present the
results of multi-dimensional calculations and discuss the role planetary and stellar
magnetic fields play in exoplanet evaporation, along with the long term impact of
evaporation on exoplanets.
Transit Transmission spectroscopy with GTC: First results
Enric Palle — Instituto de Astrofisica de Canarias
Our group is presently conducting an observational campaign, using the 10-meter Gran
Telescopio Canarias (GTC), to obtain long-slit spectra in the optical range of several
planetary host stars (and a reference star) during a transit event. The GTC instrument
OSIRIS consists of two CCD detectors with a field of view of 7.8 X 7.8 arcmin. We used
OSIRIS in its long-slit spectroscopic mode, selecting the grism R=1000 which covers the
spectral range of 520-1040 nm, and a custom-built slit of 12 arcsec of width. A Markov
Chain Monte Carlo (MCMC) Bayesian approach is used for the transit fitting, and the level
of red noise in the light curves is estimated using the method of Winn et al. (2008). Here,
we will present refined planet parameters, planet color signatures, and the transmission
spectrum of a set of know transiting exoplanets, namely: WASP-43b, HAT-P-12b,
WASP-48b, and KIC 12557548b. With our instrumental setup, GTC has been able to
reach precision down to 250 ppm (WASP-48b, V=11.06 mag) for each color light curve 15
nm wide. We will also discuss the capabilities and advantages of GTC as tool for the
follow up of faint Kepler targets, such as KIC 12557548b. The light curves obtained for this
object with low resolution gratings allow us to reach 300 ppm in a 4-min sampled curve,
thus revealing the detailed shape, small scale structures, and color information of
individual transits of KIC12557548b.
Characterisation of exoplanet atmospheres with KMOS
Hannu Parviainen — University of Oxford
We present our preliminary results and experiences with the KMOS (K-Band Multi-Object
Spectrometer) instrument in the characterisation of exoplanet atmospheres using transit
transmission spectroscopy, and detail our approach to the data reduction and analysis.
Our experiences are mainly based on transits observed during the instrument's
commissioning phase, and the investigation of the KMOS instrument's applicability to
transit spectroscopy was an important secondary goal along with the science driver.
Transit transmission spectroscopy offers a direct way to study the atmospheric properties
of transiting exoplanets. However, the variations in the transit depth are small, of order
10 -4 , and disentangling the minute changes in the transit signal from the systematic noise
signals is all but trivial.
KMOS is a NIR multi-object spectrometer capable of observing spatially resolved spectra
of 24 2.8x2.8 arcsecond freely positionable fields simultaneously. Each field is
implemented using an integral field unit (IFU) with a 14x14 pixel spatial resolution. The
ability to observe simultaneous spectra from a number of separate fields allows for high
flexibility in the selection of comparison stars for relative spectroscopy, facilitating the
reduction of common systematics. However, the use of IFUs with small spatial footprints
creates also new challenges that need to be overcome before the instrument's full
potential can be used.
Direct evidence of the inversion layer in HD 209458 b from high-dispersion
Henriette Schwarz — Leiden University
We present preliminary results from high-resolution thermal emission spectra of the hot
Jupiter HD 209458 b. This bright transiting planet is interesting because it is a good
candidate for a hot Jupiter with an inversion layer in its atmosphere. Snellen et al. (2010)
observed HD 209458 b during a transit with high-resolution spectra at wavelengths around
2.3 micron, and they detected molecular absorption from carbon-monoxide. The new dataset
again uses the CRIRES spectrograph at VLT. This time we are looking at the thermal
emission from the hot day-side of the planet at phases close to the secondary eclipse. We
see no evidence for CO absorption in the thermal spectra, but an interesting hint of CO
emission — the tell-tale sign of a thermal inversion layer high up in the atmosphere of this
Atmospheric characterization of the hot Jupiter Kepler-13b
Avi Shporer — Caltech/JPL
Kepler-13b (= KOI-13.01) is a unique transiting hot Jupiter. It is one of very few known
short-period (1.76 day) planets orbiting a bright (V~10 mag) A-type star. Therefore, it is
among the hottest and brightest planets currently known, motivating the study of its
atmosphere. The availability of Kepler data allows us to measure the planet's occultation
(secondary eclipse) and phase curve, in the optical, with very high precision, which we
combine with occultations observed by the Warm Spitzer Mission at 3.6 micron and 4.5
micron, and a ground-based occultation observation by the Wide-field Infra-Red Camera
(WIRC), mounted on the Palomar 200 inch telescope, at the Ks band (~2.1 micron). Since
the host star is the primary component of a visual binary system with ~1 arcsec separation,
the two similar stars are fully blended in all our photometry. To correct the observed
occultation depths for this dilution we modeled the stellar spectra, from the optical to the
infrared, based on Keck/HIRES spectra that resolved the two stars. Our preliminary results
indicate that the planetary atmosphere has a relatively high geometric albedo (Ag ~0.3)
and a highly efficient heat distribution from the day side to the night side (epsilon ~0.9).
This represents a deviation from previous studies in which the most highly irradiated hot
Jupiters were found to have inefficient recirculation of energy from the day to the night
sides. We also present revised atmospheric parameters for the planet-hosting star in this
triple stellar system, and a revised planetary mass estimate based on the beaming effect
and the tidal ellipsoidal distortion observed in the Kepler phase curve.
Revealing Distant Worlds with Ground-Based Spectroscopy
Kevin Stevenson — University of Chicago
Uncovering the fundamental properties of exoplanetary atmospheres requires highprecision
spectroscopy over a broad range of wavelengths. We are poised to make
significant advances in our understanding of their composition and chemistry using
currently-available, visible and near-infrared multi-object spectrographs attached to some
of the largest telescopes in the world. With facilities such as Gemini, Keck, and Magellan,
we are conducting an intensive survey of a representative sample of exoplanets to
measure their transmission and dayside emission spectra. We will present high-quality
spectra for several recently-observed exoplanets and discuss how these data constrain
the molecular abundances, thermal profiles, and relevant chemistries of these planetary
Updated Spitzer Secondary Eclipse Spectroscopy of HD189733b
Kamen Todorov — ETH Zürich
We analyze Spitzer Space Telescope time-series spectroscopy observations of HD
189733b during 18 secondary eclipses at wavelengths between 5 and 14 microns. These
measurements comprise the most extensive emission spectrum of any exoplanet to date.
While some of these data sets have been analyzed previously by Grillmair et al. (2008),
we examine eight of them for the first time. We remove the systematic effects from the
spectral light curves using the most advanced techniques available, and measure the
secondary eclipse depths as a function of wavelength. We use a modified version of a
radiative transfer code by Richardson et al. (2003) to calculate three emergent spectrum
models and compare our observational results with them, and with the best fit model
(Burrows et al. 2008) adopted by Grillmair et al. in their earlier investigation. We can
confidently exclude isothermal and gray atmospheres and confirm the water feature
detected by Grillmair et al.
Phase curves of close-in Kepler planets
Vincent Van Eylen — Aarhus University!
The Kepler satellite has provided a wealth of new data on transiting exoplanets. Its
unprecedented precision allows for more than just analyzing the transit: for hot planets in
an orbit of only a few days, the parts-per-million precision allows for the detection of
planetary light throughout the full phase, as well as its absence during the secondary
eclipse. For those tidally locked planets, the increase in received flux as we view more and
more of the planet's day side allows us to make statements on the planetary reflection
(albedo) and temperature. Measuring the depth of the occultation leads to estimates on
the temperature of the (cold) planetary nightside. I present preliminary results on a
comparative study of the sample of close in transiting exoplanets which were observed by
Water in the atmosphere of hot-Jupiter exoplanets
Hannah Ruth! Wakeford — University of Exeter
Using the Hubble Space Telescope’s WFC3 camera with an infrared low resolution grism,
we observed a number of hot Jupiters from 1.1-1.7 µm, probing primarily the H2O
absorption band at 1.4 µm. H2O is a key molecule for constraining hot-Jupiter
atmospheres with the atmospheric C/O ratio playing a pivotal role in the relative H2O
abundance. We present a variance in these hot Jupiter atmospheres with a strong H2O
detection in the upper atmosphere of HAT-P-1b and new results from WASP-31b. The
computed transmission spectra show a startling diversity in the observed abundance of
H2O in the atmosphere of close-in giant planets allowing us to explore the nature of their
The 4.5 micron phase curve of HD 209458b!
Robert Zellem — Lunar and Planetary Laboratory - University of Arizona!
The hot Jupiter HD 209458b is one of the most favorable targets for full-orbit phase curve
observations, as it is one of the brightest systems (V-mag = 7.65, K-mag = 6.308), has a
large planet-to-star contrast, and offers a high signal-to-noise ratio and the ability to make
high-precision measurements. This planet also serves as the archetype for a class of
planets that have dayside temperature inversions; the differences between this class of
planets and those lacking inversions (including HD 189733b) are currently not wellunderstood.
Here we present the first full-orbit phase curve of HD 209458b observed with
the Spitzer/IRAC 4.5 micron photometric band. Our data, which includes one primary
transit and two secondary eclipses, was reduced with a pixel-mapping method to get within
1.145 times the photon noise limit. We measure the brightness temperature of the
observed phase curve. The results are modeled with radiative transfer models along with
other primary transit and secondary eclipse data to determine the pressure level of the
emissions. We then compare these results to predictions from global circulation models,
including those where magnetic effects and thermal inversions are present in order to
determine the effect that HD 209458b\s dayside temperature inversion has on its
atmospheric circulation and chemistry.
HOT JUPITERS: MODELS
Effects of clouds on reflection properties of hot Jupiters!
Nadine Afram — Kiepenheuer Institut für Sonnenphysik, Freiburg
The presence of clouds in exoplanetary atmospheres may dramatically change their
reflectivity properties. This can be detected during secondary eclipses and with the help of
polarimetric techniques, independently of planet transits. Here, we model polarimetric
phase curves and secondary eclipses for some very hot Jupiters with orbital periods
shorter than 3 days (e.g., WASP-19b, HD189733b) using model atmospheres with and
without clouds. We empirically adjust pressure-temperature profiles and the cloud
composition and height and investigate how polarization and eclipse curves depend on
atmosphere parameters. In particular, we consider such molecules and condensates as ,
OH, H2, CO, CO2, CH4, NH3, MgO, MgSiO3, Mg2SiO4, Al2O3, etc. We compare our results with
available polarimetric and photometric measurements for hot Jupiters.
Testing radiative transfer schemes for use in global circulation models of hot
David Skålid!Amundsen — University of Exeter!
Several studies which have used adapted Global Circulation Models (GCMs) to interpret
observations of hot Jupiters have now been published. Almost all of these studies involve
simplified dynamical (e.g shallow water or primitive equations) and radiative transfer
schemes (temperature forcing, grey or band-averaged absorption coefficients). We are
adapting the UK Met Office GCM, the Unified Model, which solves the full 3D compressible
Euler equations and includes a frequency dependent radiative transfer scheme (invoking
the two-stream approximation and correlated-k method) for the study of hot Jupiters.
We will discuss the adaptation of the radiative transfer scheme and the tests we have
performed to verify its accuracy. By comparing to more accurate discrete-ordinate line-byline
calculations we will demonstrate that this scheme yields fairly accurate fluxes and
heating rates overall. In some cases, however, there are significant deviations, and we find
the use of band-averaged absorption coefficients to be very inaccurate. Lastly, I will
present some of the first results we have obtained after recoupling the dynamical core and
radiative transfer schemes.
An Open Source Python Thermochemical Equilibrium Abundances Code!
Jasmina Blecic — University of Central Florida
We present a Thermochemical Equilibrium Abundances code (TEA) that calculates the
equilibrium abundances of the molecular species present at a given temperature and
pressure in a planetary atmosphere. There are two approaches to calculating
thermochemical equilibrium: by using equilibrium constants and reaction rates or by
minimizing the free energy of the system. Although chemical equilibrium can be calculated
almost trivially for several reactions present in the system, as the number of reactions
increases, the number of equilibrium-constant relations becomes difficult to solve
simultaneously. An advantage of the free-energy-minimization method is that each
species present in the system can be treated independently, without specifying
complicated sets of reactions. Therefore, just a limited set of equations needs to be
solved. TEA is based on the Gibbs-free-energy minimization calculation, originally
developed by White et al. (1958) and Eriksson (1971). The code is written entirely in
Python and is available to the scientific community under an open-source license.
VSTAR Models of a Hot Jupiter
Kimberly Bott -- University of New South Wales
Past analysis of HD 189733b's atmosphere has been a cause for some debate, with
conflicting findings regarding polarized light, carbon dioxide and sodium abundances and
the presence of a high altitude haze. I will present our model of HD 189733b's atmosphere
using VSTAR (Versatile Software for Transfer of Atmospheric Radiation), a robust, line-byline,
multiple scattering radiative transfer solution in a modular program, utilitizing its own
chemical equilibrium model. Since the effective temperature of the planet is expected to be
approximately 1100K, newly available high-temperature spectral line lists were used. The
planet’s dayside, terminator and reflected polarized light are modeled and compared to
Circumplanetary Jet Formation, Characteristics, and Observational Diagnostics
Ian Dobbs-Dixon — University of Washington!
Ubiquitous among multidimensional simulations of highly irradiated gas-giant planets is the
development of circumplanetary jets in the equatorial region of the planet. These jets,
many of which become supersonic, are the dominant dynamical feature, helping to shape
all observable features and perhaps influencing the thermal evolution of the entire planet.
However, observations of irradiated gas-giants suggest that not all planets form such jets.
Despite their importance for interpreting observations, the precise physical mechanism for
forming and sustaining jets remains an area of active research. We lay out a linear theory
for the formation of these jets and compare our predicted behavior to results from
multidimensional radiative-hydrodynamical simulations. We then further discuss a novel
observational technique for detecting these jets during a single eclipse. A faster method of
detecting a jet will allow for a much broader survey of systems, hopefully shedding light on
the physical parameters of the system that help or hinder jet formation.
Escape of Hydrogen from HD209458b!
Justin!Erwin — University of Arizona!
Recent modeling of the atmosphere of HD209458b has been used to interpret the Lymanline
and other observations during transits. Koskinen et al. (2010) used a hydrostatic
density profile in the thermosphere combined with the Voigt profile to estimate the Lymanalpha
transit depths for an array of model parameters. A detailed photochemical-dynamical
model of the thermosphere was developed by Koskinen et al. (2013a) and used to again
estimate model parameters to fit not only the Lyman-alpha transits, but also the transits in
the O I, C II and Si III lines (Koskinen et al., 2013b). Recently, Bourrier and Lecavelier
(2013) modeled the escape of hydrogen from the extended atmospheres of HD209458b
and HD189733b and used the results to interpret Lyman-alpha observations. They
included acceleration of hydrogen by radiation pressure and stellar wind protons to
simulate the high velocity tails of the velocity distribution, arguing that the observations are
explained by high velocity gas in the system while Voigt broadening is negligible.
In this work we connect a free molecular flow (FMF) model similar to Bourrier and
Lecavelier (2013) to the results of Koskinen et al. (2013b) and properly include absorption
by the extended thermosphere in the transit model. In this manner, we can interpret the
necessity of the various physical processes in matching the observed line profiles.
Furthermore, the transit depths of this model can be used to re-evaluate the atmospheric
model parameters to determine if they need to be adjusted due to the existence of the
extended hydrogen tail.
Thor: A GPU code for simulating exoplanetry atmospheres
Simon!Grimm — University of Zürich
We present an implementation of a three-dimensional general circulation model (GSM),
designed for simulating exoplanetary atmospheres, running fully parallel on Graphics
Processing Units (GPU’s). The Code is developed for the Exoclimes Simulation Platform
(ESP) and will be available as open source software. Thor solves the three dimensional
non hydrostatic Euler equations on a modified Yin-Yang grid, which consists of an
equatorial belt and two polar caps, which are patched together using a fully conservative
zonal interface algorithm, described by Wang (1995). The individual grids are solved with a
horizontal explicit and vertical implicit (HEVI) finite difference scheme, where the vertical
solution can be computed analytically. In this poster we present the implemented scheme
and show as well results of the first tests, including a quantification of the conservation of
energy, mass and momentum.
Compared to other available CPU codes, Thor shows a speed-up of around one
magnitude. Thor is written in Cuda C and runs on all Nvidia GPU's.
The Exoclimes Simulation Platform!
Kevin! Heng! — Center for Space and Habitability, University of Bern
The state of the art in performing 3D simulations of exoplanetary atmospheres centers
around adapting GCMs (general circulation models), originally designed for the study of
Earth. These Earth-centric tools suffer from fundamental shortcomings, including Earthcentric
assumptions, the inability to model shocks, the exclusion of magnetic fields and the
treatment of radiative transfer as if the atmosphere is static. We offer an alternative
perspective: the design and development of a set of publicly available, theoretical and
simulational tools for the general exoplanet community, partly to combat the growing "black
box" culture in our field. I give a brief and broad review of the Exoclimes Simulation
Platform (ESP), focusing on the GCMs and radiative transfer tools that are currently in
development. I will also explain our decision to build the ESP entirely on GPUs, which
gives our open-source tools a speed-up of at least an order of magnitude (two orders of
magnitude for radiative transfer). I will describe how we plan to involve the community via
a web portal (www.exoclime.org), which includes a Facebook page for soliciting feedback.
VIPER: Toward a universal model for planetary climate
Nicolas Iro — University of Hamburg
With the discovery of an increasing number of planets outside our Solar System, we are
becoming familiar with physical conditions and atmospheric compositions that span a
much wider range that what covered by the planets of our solar system. Non-exhaustive
examples are equilibrium temperatures ranging from 50K (Neptune) to over 3000K
(WASP-12b, WASP18b); orbital eccentricity, ranging from 0-0.1 for solar system planets
(except Mercury) and circularized close-in hot Jupiters to e = 0.93 (HD80606b). Other
parameters relevant for atmospheric dynamical features are also quite diverse: the Rhines
length and Rossby length are, e.g., much smaller than the planet radii for Solar-System
planets, while they are comparable to the planetary radii for hot Jupiters and Neptunes,
meaning that in the latter case typical circulation features are global. It seems timely and
urgent to try to frame in a common framework our understanding of such a large variety of
atmospheric conditions. We will present VIPER, the Versatile Interactive PlanetSimulator
for Extrasolar Research. This project, under development, aims at developing the Planet
Simulator, an already flexible climate model to a new level of modularity. In the next phase
of the implementation, we will remove all parameterization pertaining to Earth, allowing for
instance to study any planetary rotation rate and add a simple yet precise radiative
scheme based on the k-distribution coefficients. This will allow us to model the climate on
a variety of planetary conditions from early Mars to Super-Earths.
Modelling of the Emission Spectrum of WASP-19b
Lucyna Kedziora-Chudczer — University of New South Wales
The VSTAR radiative transfer code was used to model the emission spectrum of the one
of the most irradiated hot-Jupiters, WASP-19b. We examined models with different
pressure-temperature profiles and C/O abundances ratios. We find that models with
carbon enrichment above solar match the available data best. We also included upperatmosphere
haze of varied particle sizes and find that particles
ongoing. This will help us understand, for given circumstances, how a planetary magnetic
field could alter the wind structure on hot Jupiters and its effects on day-night temperature
variations and planetary radii.
Extended ionospheres on extrasolar giant planets!
Tommi! Koskinen — University of Arizona
Recent work on close-in extrasolar giant planets (EGPs) raises the possibility that their
atmospheres are significantly affected by ion drag and Joule heating arising from thermal
ionization of their atmospheres (e.g., Cho 2008, Batygin et al. 2010, Perna et al. 2010a,b).
It is unclear, however, if large scale current systems are supported in the relatively weakly
ionized atmospheres of close-in EGPs. We explore thermal ionization and photoionization
of EGP atmospheres, and use the results to constrain the electrodynamic regimes at
pressures ranging from 1 bar to the escaping thermosphere. In line with planetary
atmospheres in the solar system, we find that the coupling of the ions to the neutral
atmosphere is important at all pressure levels. Assuming a magnetic field similar to that of
Jupiter, we find that both the electrons and ions are collisionally coupled to the neutrals
below the 0.1-1 mbar level, but significant ion drag and Joule heating are possible at
pressures lower than this. The conductivities that we calculate, however, imply that the
upper atmospheres of close-in EGPs occupy a regime closer to the solar chromosphere
than planetary ionospheres in the solar system — even at relatively high pressures in the
stratosphere. Nevertheless, the generalized Ohm’s law for partly ionized media is still
valid and we explore the resulting current systems based on this assumption.
3-D modeling of atmospheric escape from Hot Jupiters !
Alain Lecavelier — Institut d'Astrophysique de Paris!
Transit observations in the Lyman-alpha line of the hot Jupiters HD209458b and
HD189733b revealed strong signatures of neutral hydrogen escaping the planet's
atmospheres. We will present our 3D particle model of the dynamics of the escaping
atoms, which is used to calculate theoretical absorption profiles, and can be directly
compared to the observations to constrain the physical conditions at high altitudes in the
exosphere (such as the escape rate and the stellar ionizing flux). Recently, this model has
also been used to interpret the observation of neutral magnesium probing the
thermosphere-exosphere transition region. Simulations show the major influence of the
stellar radiation pressure on the structure of the escaping gas cloud, which can also be
shaped by stellar wind interactions, planetary gravity and self-shielding effects. This results
in spectro-temporal variations of the absorption profile that could be used to further
characterize the atmospheric escape. On a wider scale, our model can be used as a
predictive tool to identify evaporating exoplanets with high-significance absorption
Non-hydrostatic, deep-atmosphere hot Jupiter climate models
Nathan Mayne — University of Exeter!
We present results for the climate of hot Jupiter HD209458b derived using a global
circulation model (GCM) which, using the same numerical scheme, can solve both the full
unsimplified dynamical equations for a rotating atmosphere, as well as including increasing
simplification to these equations. Our results show that the bulk atmospheric flow is largely
obust to the canonical simplifications if short integration times and small vertical domains
are used (i.e. shallow weather layers). However, for longer integrations and models
incorporating a “deeper” (i.e. larger in vertical extent) atmosphere such simplifications to
the dynamical equations produce different flows. We also explore the changes to the
driving, or pumping, mechanisms for the large scale flow features in the atmosphere under
improvements to the dynamical description. We have also adapted a more complete
radiative transfer scheme for the physical conditions of hot Jupiters and I will outline
progress coupling this to the dynamical code.
Chemical disk evolution and element abundances of gas giants
Peter Woitke — St. Andrews University!
We discuss the chemical pre-conditions for planet formation, in terms of gas and ice
abundances as function of time and position in a protoplanetary disk. Considering the
standard core-accretion model for planet formation, the overwhelming majority of the mass
of the gas giant will only be accreted onto the proto-planet in a final rapid run-away phase,
using up the remaining gas in the planet feeding zone. This gas will contain only traces of
refractory elements, and possibly only little amounts of elements like C, N and O, which
may have frozen out as ices before. ProDiMo protoplanetary disk models are used to
predict the chemical evolution of gas and ice in the midplane. We find that cosmic rays
play a crucial role in slowly un-blocking the CO, where the liberated oxygen forms water
which freezes out quickly. Therefore, the carbon-to-oxygen ratio C/O in the gas phase is
found to gradually increase with time in the disk, in a region bracketed by the water and
CO ice-lines. C/O is found to exceed unity after about 7 Myrs, scaling with the cosmic ray
ionization rate assumed.
YOUNG GIANT PLANETS AND BROWN DWARFS
A radiative-convective equilibrium model for young giant exoplanets: Comparison
with observations and other existing models
Jean-Loup Baudino — LESIA, Observatoire de Paris!
We developed a radiative-convective equilibrium model for young giant exoplanets. Input
parameters are the planet's surface gravity (g), effective temperature (Teff) and elemental
composition. Under the additional assumption of thermochemical equilibrium, the model
predicts the equilibrium temperature profile and mixing ratio profiles of the most important
gases. Opacity sources include the H2-He collision-induced absorption and molecular lines
from H2O, CO, CH4, NH3, VO, TiO, Na and K. Line opacity is modeled using k-correlated
coefficients pre-calculated over a fixed pressure-temperature grid. Absorption by iron and
silicate cloud particles is added above the expected condensation levels with a fixed scale
height and a given optical depth at some reference wavelength. Scattering is not included
at the present stage. Model predictions are compared with the existing photometric
measurements of Planet Beta Pictoris b and Kappa And b in the J, H, Ks, L', NB 4.05, M'
bands and with spectroscopic observations of the HR8799 planetary system to constrain
Teff and g. Finally, our results are compared with those derived from other existing models.
This model will be used to interpret future photometric and spectroscopic observations of
exoplanets with SPHERE, mounted at the VLT with a first light expected in 2014.
Spitzer and z' Secondary Eclipse Observations of the Highly Irradiated Transiting
Brown Dwarf KELT-1b!
Thomas Beatty — Ohio State University!
KELT-1b is a highly-irradiated, highly-inflated, 27 Jupiter-mass object transiting a bright
(V=10.8) F5V star with a period of 1.2 days. KELT-1b offers a unique opportunity to study
the atmosphere of a brown dwarf with known mass, radius, and approximate age, in a
radiation environment similar to hot Jupiters. We present and discuss secondary eclipse
observations of this system taken using the Spitzer Space Telescope and from the ground.
We measure secondary eclipse depths of 0.196+/-0.01% at 3.6 μm and 0.200+/-0.012% at
4.5 μm, corresponding to a fairly grey color of [3.6]-[4.6] = 0.07+/-0.11. Using four separate
ground-based light curves, we find suggestive evidence for the secondary eclipse in the z
band with a depth of 0.046+/-0.023%. These observations represent the first constraints
on the atmospheric dynamics of a highly-irradiated brown dwarf, and are interesting in the
context of both the atmospheres of irradiated giant planets at high surface gravity, and the
atmospheres of brown dwarfs that are dominated by external, rather than internal, energy.
In particular, as compared to objects of similar temperature, KELT-1b has a [3.6]-[4.6] color
that is similar to isolated brown dwarfs, in contrast to lower surface gravity exoplanets,
which tend to have redder colors.
Critically testing atmospheric models with benchmark brown dwarfs
Ben Burningham — University of Hertfordshire
The current generation of wide-field surveys is probing such a volume that significant
numbers of brown dwarfs are being identified as rare wide common proper motion binary
companions to higher mass stellar primaries. If such systems are formed in the same
manner as similarly separated stellar binaries then it follows that the composition and age
of the primary may be used to infer the same properties for the low-mass companion,
making such systems attractive calibrators for substellar and exoplanetary atmospheric
(spectral) model grids. They are thus referred to as benchmark systems. In this
contribution, I will discuss recent results from our search for substellar benchmarks,
focusing on how the emerging grid of calibrated atmospheres can be used to provide new
insights into the strengths and deficiencies of differing model approaches, and highlighting
how benchmark systems have revealed that metallicity is as important as effective
temperature for determining the SED of cool substellar objects. Finally, I will explore how
the potential of benchmark brown dwarfs for breaking observational degeneracies can be
realised to solve key science goals in exoplanetary science.
Doppler imaging of a Nearby Cloudy Brown Dwarf
Ian Crossfield — MPIA
Brown dwarfs provide easily-observable analogues to young extrasolar planets with similar
temperatures and radii but lower masses. Brown dwarfs are the first substellar objects for
which cloud-induced temporal variability has been observed, but so far the
characterization of these complex & dynamic atmospheres has been limited to lowresolution
spectroscopy and photometry. We will present Doppler Imaging of a brown
dwarf’s surface using high-resolution near-infrared spectroscopy. Future such observations
will track the formation, evolution, and breakup of global weather patterns, and will provide
revolutionary new benchmarks against which to compare global circulation models of
cloudy substellar objects.
Ionisation regimes structuring planetary atmospheres!
Christiane Helling — University of St Andrews!
The steady increase of the sample of extrasolar planets broadens our knowledge and at
the same time, reveals our lack of understanding fundamental processes. For example
does the habitability of a planet depend, amongst other things, on how much and which
radiation reached the ground, how clouds form and which effect clouds have on the
composition and on the electric state of the ambient gas from which they form.
We have studied the formation of mineral clouds on planetary atmospheres by a kinetic
approach which allows us to predict the size distribution and material composition of the
cloud particles. These results have been used to study if such clouds can be charged and
under which conditions an electric field breakdown, such as lightning or other transient
luminous events, may occur. Our results suggest that different intra-cloud discharge
processes dominate at different heights inside a cloud, and that the atmospheric volume
affected by large-scale lightening discharges is larger in Brown Dwarfs than in planetary
atmospheres. We demonstrate how different ionisation processes suggest that planets and
brown dwarfs have stratified ionised atmospheres.
Atmospheric cloud models from brown dwarfs to exoplanets
Derek Homeier -- Centre de Recherche Astrophysique de Lyon/ENS-Lyon!
State-of-the-art theoretical models of low-mass stars and brown dwarf atmospheres aim at
a physically and chemically consistent simulation, generally evolving from the assumptions
of hydrostatic and radiative equilibrium as well as a chemical equilibrium composition
based on given input abundances. In further refinement more complex phenomena such
as atmospheric dynamics and departures from chemical equilibrium by advection,
photochemistry or condensate formation can be considered. This approach has allowed
model grids based on a minimal set of parameters to reproduce observed properties of
substellar objects with considerable success. Most important among these is without doubt
the role of cloud opacity throughout the sequence from late-type stars to the coolest brown
dwarfs known to date. I will present the results of the PHOENIX Settling models, which
successfully describe the formation of different cloud types, from iron and silicate dust
dominating in L dwarfs over sulphides and halides that become relevant in cooler T dwarfs,
to the appearance of water ice and colder condensates in the latest Y dwarfs. These
models can often be applied with little modification to lower mass objects such as directly
imaged gas giants, highlighting the effects of lower gravity on atmospheric chemistry and
cloud formation. However, as one explores more fully the domain of exoplanet
atmospheres, increased complexity like global transport triggered by irradition, and
atmospheric chemistry no longer based on scaled-solar compositions come into play.
Consequently the direct retrieval of atmospheric properties from observed data, is often
preferred in these cases, but with only few data points to constrain the models, may
struggle to produce a unique and physically realistic solution. I shall show here how our
models can still be applied in this context to hot Neptunes and super-Earths to place
constraints on atmospheric properties using the most recent transit spectroscopy results.
New insights on beta Pictoris: discovery of two different populations
Flavien Kiefer — Institut d'Astrophysique de Paris!
High-resolution spectroscopic observations of beta Pictoris made with HARPS bring new
information on the exocomets falling onto the star (FEB scenario). With more than a
thousand spectra gathered between 2003 and 2011, we have around 6000 variable
absorptions detected. Using this huge catalogue of events we achieved an unprecedented
statistical and temporal study of beta Pic comets. We will present the results of this
statistial analysis, and display the evidence that allowed us to discover two very different
populations of comets in this young planetary system.
Magnetic fields on L-type brown dwarfs!
Oleksii Kuzmychov — Kiepenheuer-Institut für Sonnenphysik
Several rapidly-rotating L-type dwarfs exhibit transient but periodic radio pulses that are
possibly driven by electron-cyclotron maser (e.g., Hallinan et al. 2007, 2008). For this
mechanism to work, a few kG magnetic field is required. In order to examine whether
these objects possess such a strong magnetic field, we model polarized spectra of L-type
brown dwarfs including transitions in diatomic molecules, such as CrH, FeH, and TiO. We
compare these synthetic spectra with full Stokes spectra of two brown dwarfs measured at
several rotational phases using the low-resolution spectropolarimeter LRIS at the Keck
Observatory in August 2012. We are able to constrain the magnetic field strength in these
objects and discuss implications of our results.
Spectral Retrieval Analysis of the Directly Imaged exoplanets around HR 8799
Jae-Min Lee — University of Zurich
The direct-imaged exoplanets around HR 8799 are photometrically distinct from their
parent star. Spectroscopic measurements along with photometric points between 1 and 5
µm provide vital information on the thermal and chemical structure of the atmosphere,
which have never been achieved from transiting exoplanets. However, it is still mysterious
that the characteristics of the atmosphere show a mixture of brown dwarf and gas giant
features, calling its radius, surface gravity and mass into a question. Here, we perform
inverse modelling by exploiting an optimal estimation retrieval technique and sweep the
parametrized radius and surface gravity space with phenomenological cloud scenarios.
Unlike previous approaches, in which the cloud models are rather sophisticated, we
minimise the number of cloud parameters, e.g., mono-disperse cloud particle size and
optical depth of cloud. We find that the identity of the cloud material gives a non-detectable
effect to our results because the refractive indices of most of materials plausible in this
class of atmosphere are not distinguishable at these wavelengths. Also, we report physical
properties of these planets, such as radius, surface gravity and mass, which can provide
useful constraints for building its formation scenario.
A Comparison of Exoplanet Atmospheric Retrieval Techniques
Michael Line!— University of California Santa Cruz
Secondary eclipse spectra allow us to infer the temperatures and compositions of
exoplanet atmospheres. A variety of statistical approaches exist to determine the most
probable set of temperatures and compositions such as Markov Chain Monte Carlo and
Optimal Estimation. I will give an overview of these approaches in the context of the
Bayesian formalism and discuss the similarities and differences in their derived posterior
probabilities. I will show in which regimes optimal estimation is appropriate and in which
regimes MCMC approaches are necessary. Finally, as a side, I will discuss the potential
pitfalls of statistical determinations of the atmospheric C/O ratio.
Young and Planetary-Mass: Connecting Low-Gravity Field Brown Dwarfs and
Directly Imaged Gas-Giant Planets!
Michael Liu — University of Hawaii, Institute for Astronomy!
Direct detections of young gas-giant exoplanets and recent identification of very young
field brown dwarfs are strengthening the observational link between the exoplanet and
brown dwarf populations, enriching our understanding of both classes of objects. However,
studies to date have typically focused on individual discoveries. We present a large
comprehensive study of the youngest field brown dwarfs, comprising both previously
known objects and our new discoveries from the Pan-STARRS-1 wide-field survey. These
objects have physical properties that overlap young gas-giant planets and thus are
promising analogs for studying exoplanet atmospheres at high S/N and spectral resolution
down to ~5 Jupiter masses. We combine high-quality spectra and parallaxes to study their
spectral energy distributions, luminosities, temperatures and ages. We demonstrate that
the peculiar IR colors and magnitudes of the planets around 2MASS J1207-39 and HR
8799 do occur in some young brown dwarfs, but these properties do not have a simple
correspondance with age. We find that young field brown dwarfs can have unusally low
temperatures (but they are not underluminous, as often claimed). To help provide a
reference for upcoming extreme-contrast imaging surveys, we establish a grid of spectral
standards and benchmarks, based on membership in nearby young moving groups, in
order to calibrate gravity (age) and temperature diagnostics in near-IR spectroscopy.
Finally, we use our data to critically examine the possibility that free-floating objects and
companions may share different evolutionary histories, thereby complicating the "brown
MagAO/VisAO Optical Imaging of beta Pictoris b: A Comparative Study of
Exoplanets and Brown Dwarfs!
Jared! Males — University of Arizona
We used the Magellan AO system's visible wavelength diffraction limited camera, VisAO,
to image the ~10 Jupiter mass exoplanet beta Pictoris b. This is the first ground-based
direct image of an exoplanet at wavelengths less than 1 micron. Using our photometry,
combined with existing JHK measurements, we compare beta Pic b to field brown dwarf
spectra. Our analysis yields a rigorous empirical determination of the planet's spectral
type, and through this an estimate of effective temperature. Our photometry highlights the
extreme diversity amongst the directly imaged extrasolar giant planets and both field and
companion brown dwarfs, yet points to remarkable similarities in formation and evolution
despite this diversity.
Comprehensive Results from the Weather on Other Worlds Spitzer Campaign:
Photometric Variability Is Ubiquitous on L and T Dwarfs
Stanimir Metchev — Western University!
I will present the first comprehensive results from the ""Weather on Other Worlds"" Spitzer
Exploration Science program: the most precise and comprehensive study of cloud-induced
photometric variability in L and T dwarfs. We observe that 45% of L3-T8 dwarfs are
variable, with amplitudes between 0.2%-5% at 3.6 and 4.5 micron. Contrary to
expectations, the variability fraction is independent of spectral type, suggesting that cloud
phenomena are present in ultra-cool dwarfs over the entire 700-2000 K effective
temperature range surveyed in our program, and likely at even cooler temperatures.
Combined with spin-axis and cloud/hole viewing geometry considerations, our findings
indicate that cloud-induced variability is present on virtually all L3-T8 dwarfs. If the
detected variability is caused by single large storms, rather than by multiple smaller ones,
the measured amplitudes and temperature contrasts indicate that these features cover
between 8%-40% of the visible disks of brown dwarfs. That is, atmospheric storms with
sizes between approximately half to twice that of the Great Red Spot on Jupiter are
ubiquitous on 700-2000 K brown dwarfs.
Water Clouds in Y Dwarfs and Exoplanets!
Caroline Morley — University of California Santa Cruz!
A major frontier in the fields of directly imaged planets is finding and characterizing the
coolest known objects. For planets with effective temperatures below about 450 K, it has
long been known that water clouds will form and shape the infrared spectra of these
objects. However, no previous modeling studies have systematically shown the effect that
water clouds will have on the spectra of these cold planetary-mass objects. Within 1-2
years, GPI and SPHERE will be able to directly image and characterize planets down to
~300 K, so the time is right to better understand cool atmospheres dominated by water
Cold brown dwarfs will also contain water clouds and they provide a test-bed for our new
generation of cloudy atmosphere models. The newly-proposed spectral type Y includes
brown dwarfs cooler than about 500 K, many of which will have water clouds. Over a
dozen Y dwarfs have now been discovered and are beginning to be characterized;
followup studies by various groups aim to measure their spectra, monitor them for
variability, and measure their parallaxes. The models presented here will allow us to
determine the physical properties of the Y dwarfs and allow us to compare the brown dwarf
population to directly-imaged planets as they are discovered.
Here we present a study of clouds in objects that bridge the gap between brown dwarfs
and solar-system planets, with effective temperatures from 200 to 500 K. We present
results for both planetary-mass objects and for Y dwarfs and compare models to available
Y dwarf spectra to test their validity. We make predictions for the spectra, colors, and
magnitudes of young giant planets and the Y dwarf population. We also predict the level of
variability expected in the near- and mid-infrared.
Direct imaging of exoplanets: Remote sensing of planetary systems and processes
Katie Morzinski — University of Arizona!
Beta Pictoris hosts a planet at sub-arcsecond separation, detected via high-contrast
imaging. We observed Beta Pic b at first-light of the new Magellan adaptive optics
instrument "MagAO" in December 2012, simultaneously with our visible-light and infrared
cameras. I will present my MagAO imaging data of Beta Pic b at 5 passbands, providing a
fuller picture of the planet's spectral energy distribution. This broad wavelength coverage
will be crucial to determining the energy balance of new exoplanets as improved AO
technology allows direct imaging to probe closer separations and lower masses. MagAO is
unique in achieving diffraction-limited imaging from 0.6-5 microns, and will be vital to
characterizing these planetary systems.
The Mid-Infrared Properties of Directly-Imaged Exoplanets
Andrew Skemer — University of Arizona!
Self-luminous exoplanets emit the majority of their photons in the mid-infrared (>3 micron).
However, the difficulty of working in the thermal infrared from the ground has precluded the
detailed studies of exoplanets at these longer wavelengths.
Using the low-emissivity adaptive optics systems at the LBT and Magellan, we present 6
new photometric points on the HR 8799 planets and 1 new photometric point on 2M1207
b. These data probe the 3-4 micron region where previous studies have found a 1-2
magnitude discrepancy between their atmospheres and field brown dwarfs. For the HR
8799 planets, we find a shallow 3-4 micron slope with only a hint of possible absorption in
the methane 3.3 micron fundamental absorption band (possibly indicating the presence of
patchy clouds). For 2M1207 b we find a similar if more extreme behavior, with no sign of
The study has implications for understanding the broad properties of extrasolar giant
planets, and suggests that future mid-infrared direct-imaging searches (particularly JWST)
may need to reconsider their search strategy.
A large near-IR photometric monitoring survey of 69 ultracool L &T brown dwarfs
Paul Anthony!Wilson — University of Exeter
As the brown dwarf atmosphere cools through the L-T spectral sequence a rapid shift from
the red to the blue colours are observed across the L-T type transition. This shift in colour
happens across a narrow effective temperature range, which is hard for 1-D atmosphere
models to currently reproduce. Patchy clouds might be the explanation of the rapid change
in colour observed over a narrow temperature range. The consequence of patchy clouds
would be variations in the observed flux due to the rotation and evolution of the clouds.
I will present the results from our large near-IR photometric monitoring campaign which
covers 69 ultracool L & T type brown dwarfs. In particular I will discuss the frequency and
amplitude of variability across the different spectral types highlighting that our survey finds
new large amplitude variables across the L - T spectral range showing no preference for
the transition. I will also talk about observing variability at the much cooler T-Y transition.
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The conference was organised with the
support of the University of Exeter