The Program on Extrasolar Planets

The detection of Earth-sized planets is a major challenge that will be one of the great achievements in astronomy. It forms part of 'step by step' approach towards the detection of extraterrestrial life, where the steps are:

• giant planets
• terrestrial planets
• spectroscopic analysis of the planets and their atmosphere
• refining this analysis for the detection of signals of biologic activity

The first objective - giant planets- was achieved with the discovery of the planet 51 Peg B in 1995. Since then, over 100 giant planets have been found. To pass the second step - terrestrial planets - CoRoT is the first mission in preparation, with others like 'Kepler' (NASA) or 'Eddington' (of the European Space Agency) being followed. The 'transit' or 'occultation' method used by CoRoT allows the precise determination of the orbit and the size of a planet. Possibly, some of the planets found that way may later be studied spectroscopically to determine the composition of their atmosphere and the color and temperature of their surface.

Currently, we don't know the size distribution of terrestrial planets - we don't even known for certain if they exist outside of our Solar System. CoRoT pretends to prove the 'existence theorem'. This information is decisive for future projects which will perform spectroscopy of terrestrial planets, although it isn't an objective of CoRoT to select a sample for these missions. CoRoT can only detect planets that are in orbits which produce transits, and will observe a large number of stars that are relatively far away, about 1500 light years. If we assume that the distribution of planets 1500 light years away is similar then around nearby stars, this will be very useful for searches that will be organized in the future.

In any case one has to take into account that CoRoT isn't a mission primarily dedicated to find extrasolar planets, for which it isn't designed - especially due to the small size of its telescope. But certainly, realizing very high precision photometry allows CoRoT to include the search for extrasolar planets among its objectives, and to obtain very interesting informations about them.