03-12-10 'Super-Earth' atmosphere measured

The atmosphere surrounding a "super-Earth" extrasolar planet has been measured for the first time.The planet,GJ 1214b,is three times larger than Earth and about seven times heavier,and is the first planet of its kind known to have an atmosphere.Researchers reporting in Nature have said it appears to have either a dense atmosphere of water steam,or is wrapped in thick clouds like Venus.More experiments measuring more colours of light will bear out which it is.The method used could be used on many ground-based telescopes to yield atmospheric data on other exoplanets.It works by canceling out the disruptive effects of the Earth's atmosphere while that of far-flung worlds is measured from the ground.GJ 1214b was first discovered just 40 light-years away in November 2009 and has since become a focus for exoplanet research." 'Super-Earths' are really interesting,they're at the forefront of what's going on in exoplanet research," said Jacob Bean,the Harvard-Smithsonian University Center for Astrophysics scientist who led the research."They're an interesting regime because they're defined as being the transition from terrestrial planets like Earth,Venus and Mars,up to the ice giants like Uranus and Neptune."Dr Bean and his colleagues used the same "transit method" to probe the planet's atmosphere that was used to discover it.When a planet passes between its host star and the Earth,it blocks some of the star's light - how much light is blocked gives an indication of the planet's radius.Now the team has used the Very Large Telescope in Chile to see if specific colours of infrared light are blocked;the atmosphere should absorb specific colours that give away the chemicals from which it is made.From what is known about GJ 1214b,three theories of its composition and atmosphere dominated. It could either be covered in a dense layer of steam,or it could be an icy,rocky world with a hydrogen or helium atmosphere,or perhaps a large rocky planet with a mixture of volcanic gases.