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Astronomy in the News

Mercury Spring 2010 Table of Contents


This artist’s impression shows the transiting exoplanet Corot-9b.

This artist’s impression shows the transiting exoplanet Corot-9b.
Credit: ESO / L. Calçada.

First Temperate Exoplanet

European Southern Observatory

Combining observations from the CoRoT satellite and the ESO HARPS instrument, astronomers have discovered the first
"normal" exoplanet that can be studied in great detail. Designated Corot-9b, the
planet regularly passes in front of a star similar to the Sun located 1500 light-years away from Earth towards the constellation of Serpens (the Snake).

"This is a normal, temperate exoplanet just like dozens we already know, but this is the first whose properties we can study in depth," says Claire Moutou, who is part of the international team of 60 astronomers that made the discovery. "It is bound to become a Rosetta stone in exoplanet research."

"Corot-9b is the first exoplanet that really does resemble planets in our solar system," adds lead author Hans Deeg. "It has the size of Jupiter and an orbit similar to that of Mercury."

"Like our own giant planets, Jupiter and Saturn, the planet is mostly made of hydrogen and helium," says team member Tristan Guillot, "and it may contain up to 20 Earth masses of other elements, including water and rock at high temperatures and pressures."

Corot-9b passes in front of its host star every 95 days, as seen from Earth. This "transit" lasts for about 8 hours, and provides astronomers with much additional information on the planet. This is fortunate as the gas giant shares many features with the majority of exoplanets discovered so far.

More than 400 exoplanets have been discovered so far, 70 of them through the transit method.


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