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International Year of Astronomy - IYA2009
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How do we know that planets exist outside our Solar System?
Even in ancient times, people observed the planets that orbit our Sun. Nowadays we know that there are many trillions of other stars in the Universe. It seems likely that planets orbit many of these stars too. The evidence that extrasolar planets exist was obtained for the first time in the 1990s. However, these planets are small, non-luminous bodies that are light years away – how are we able to prove that they exist?
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Last update: 02/11/2009 10:04:59