ESA Science & Technology08-Jul-2005 11:26:59

Extrasolar Planets


A technique related to the radial velocity detection is to precisely measure the position of a star, so that any wobbling can be directly detected. Such observations are known as astrometry. From Earth's surface they too are restricted by the atmosphere.

ESA's Gaia mission is designed to be the most precise astrometric satellite ever created and will survey 1 billion stars after its launch, early next decade. Among a great many other scientific goals, Gaia is expected to find between 10 000 and 50 000 gas giant planets beyond our Solar System.

Once again, however, the wobbling motion caused by an Earth-sized planet will be too small to be detectable, even by Gaia.

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