Astronomy Question of the Week: 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, in addition to the Sun. It seems likely that planets orbit many of these stars too.
The evidence that extrasolar planets (exoplanets for short) exist was obtained for the [...]

Full story at http://spacefellowship.com/2009/10/12/astronomy-question-of-the-week-how-do-we-know-that-planets-exist-outside-our-solar-system/