Report - School of Physics

number of individual 1–2 m s −1 measurements. The feasibility of this proposal is
addressed in Section 1.3.
The Hypertelescope Path (Labeyrie): Appendix B provides an introduction to
the concepts and goals of the ‘densified pupil multi-aperture imaging interferometer’
or ‘hypertelescope’. The proposal refers to the fact that space testing of versions
as small as 20 cm mirror diameter, with mass below 0.5 kg, could be considered.
Progressive versions could be used to study stellar surface resolution (20 cm apertures
spanning 100 m in geostationary orbit); detection of exo-Earths at visible and
infrared wavelengths (spanning a few hundred metres at L2); much larger versions
will be needed to resolve surface features of exo-Earths.
Lamarck – an International Space Interferometer for Exo-Life Studies
(Schneider): the proposal stresses the importance of the optical (rather than
infrared) domain for space interferometry, and outlines a concept for a temporaily
‘evolving’ interferometric station, with the participation of other countries like
China, Japan, India and Russia, employing an initial collecting area of around 40 m 2 ,
baselines above 3 km, a spectral range of 0.3–3 µm and R = 100. The mission strategy
would be to detect Earth-like planets with baselines up to 1 km, imaging of the
most promising candidates with very long baselines, then interferometer upgrades
with subsequently-launched free flyers.
The resulting recommendations of the ESA Astronomy Working Group are contained
in ASTRO(2004)18 of 19 Oct 2004. The 47 responses were assigned to three
themes: (1) Other worlds and life in the Universe; (2) the early Universe; (3) the
evolving violent Universe. The relevant part of the document is reproduced here
verbatim:
1.1 From exo-planets to biomarkers
After the first discovery of an extra-solar planet in 1995, there has been steady progress
towards detecting planets with ever smaller masses, and towards the development of a
broader suite of techniques to characterise their properties. There is no doubt that this
trend will continue into the next two decades, as substantial technological challenges are
progressively overcome. After Corot will have opened the way to telluric planet finding, the
Eddington mission would get a first census of the frequency of Earth-like planets. Gaia will
deliver important insights into the frequency of giant planets; the existence and location of
such planets is crucial for the possible existence of Earth-like planets in the habitable zone.
Gaia will also further improve our understanding of the stellar and Galactic constraints
on planet formation and existence.
The next major break-through in exo-planetary science will be the detection and detailed
characterisation of Earth-like planets in habitable zones. The prime goals would be to
detect light from Earth-like planets and to perform low-resolution spectroscopy of their
atmospheres in order to characterise their physical and chemical properties. The target
sample would include about 200 stars in the Solar neighbourhood. Follow-up spectroscopy
covering the molecular bands of CO 2 , H 2 O, O 3 , and CH 4 will deepen our understanding
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