Air Quality and Climate in Megacities and Regional Hot Spots

The darkest known exoplanetdistant gas giant the size of Jupiter11 August 2011.- Astronomers havediscovered the darkest known exoplanet– a distant, Jupiter-sized gas giantknown as TrES-2b. Measurementsshow that TrES-2b reflects less than onepercent of the sunlight falling on it, makingit blacker than coal or any planet ormoon in our solar system.TrES-2b orbits its star at a distanceof only five million kilometres. The star’sintense light heats TrES-2b to a temperatureof more than 1000 degreesCelsius. Its exotic atmosphere containslight-absorbing chemicals like vaporizedsodium and potassium, or gaseous titaniumoxide. Yet none of these chemicalsfully explain the extreme blackness ofTrES-2b.“It’s not clear what is responsiblefor making this planet so extraordinarilydark”, stated co-author David Spiegel ofPrinceton University. “However, it’s notcompletely pitch black. It’s so hot that itemits a faint red glow, much like a burningember or the coils on an electricstove”.Kipping and Spiegel determined thereflectivity of TrES-2b using data fromNASA’s Kepler spacecraft. Kepler is designedto measure the brightnesses ofdistant stars with extreme precision.TrES-2b orbits the star GSC 03549-02811, which is located about 750 lightyearsaway in the direction of the constellationDraco.ReferenceThe distant exoplanet TrES-2b, shown here in an artist’s conception, is darker than the blackest coal.This Jupiter-sized world reflects less than one percent of the light that falls on it, making it blackerthan any planet or moon in our solar system. Astronomers aren’t sure what vapours in the planet’ssuperheated atmosphere cloak it so effectively. Credit: David A. Aguilar (CfA)“Detection of visible light from thedarkest world”, Kipping D. M. and SpiegelD. S., Monthly Notices of the RoyalAstronomical Society, in press.Royal Astronomical Society(RAS)This research has been acceptedfor publication in the Monthly Notices ofthe Royal Astronomical Society and isavailable online. A preprint can be seenat http://www.astro.princeton.edu/~dsp/PrincetonSite/Home_files/darkest_world.pdfPlate tectonics may control reversals in the Earth’smagnetic field21 October 2011.- The Earth’s magneticfield has reversed many times atan irregular rate throughout its history.Long periods without reversal havebeen interspersed with eras of frequentreversals. What is the reason for thesereversals and their irregularity? Researchersfrom CNRS and the Institutde Physique du Globe(1) have shednew light on the issue by demonstratingthat, over the last 300 million years, reversalfrequency has depended on thedistribution of tectonic plates on the surfaceof the globe. This result does notimply that terrestrial plates themselvestrigger the switch over of the magneticfield. Instead, it establishes that althoughthe reversal phenomenon takesplace, in fine, within the Earth’s liquidcore, it is nevertheless sensitive to whathappens outside the core and more specificallyin the Earth’s mantle. This workis published on 16 October 2011 in GeophysicalResearch Letters.The Earth’s magnetic field is producedby the flow of liquid iron within itscore, three thousand kilometers belowour feet. What made researchers thinkof a link between plate tectonics andthe magnetic field? The discovery thatconvective liquid iron flows play a rolein magnetic reversals: experiments andmodeling work carried out over the lastfive years have in fact shown that a reversaloccurs when the movements ofTHE EGGS 18 back to contents