
© ESO/L. CalçadaThis artist’s impression shows the super-Earth exoplanet orbiting the nearby star GJ 1214.
The atmosphere around a super-
Earth exoplanet has been analyzed for the first time by an international team of astronomers using ESO's Very Large Telescope. The planet, which is known as
GJ 1214b, was studied as it passed in front of its parent star and some of the starlight passed through the planet's atmosphere. We now know that the atmosphere is either mostly water in the form of steam or is dominated by thick clouds or hazes. The results appear in the 2 December 2010 issue of the journal
Nature.The planet GJ 1214b was discovered in 2009 using the
HARPS instrument on ESO's 3.6-meter telescope in Chile. Initial findings suggested that this planet had an atmosphere, which has now been confirmed and studied in detail by an international team of astronomers, led by Jacob Bean (Harvard - Smithsonian Center for Astrophysics), using the FORS instrument on ESO's Very Large Telescope.
"This is the first super-Earth to have its
atmosphere analyzed. We've reached a real milestone on the road toward characterizing these worlds," said Bean.
GJ 1214b has a radius of about 2.6 times that of the Earth and is about 6.5 times as massive, putting it squarely into the class of exoplanets known as super-Earths. Its host star lies about 40 light-years from Earth in the constellation of
Ophiuchus (the Serpent Bearer). It is a faint star, but it is also small, which means that the size of the planet is large compared to the stellar disc, making it relatively easy to study. The planet travels across the disc of its parent star once every 38 hours as it orbits at a distance of only two million kilometers: about seventy times closer than the Earth orbits the Sun.