Space Book

Exoplanets

This chapter describes extrasolar planets, which are planets orbiting stars outside our solar system. The first extrasolar planet discovery was confirmed in 1992, although they had been predicted long before. Planets are difficult to detect directly because they are so much dimmer than the stars they orbit. The Sun is a billion (109) times brighter than Jupiter and 10 billion (1010) times brighter than the Earth. Over 3,500 extrasolar planets have been discovered as of autumn 2012. Astronomers use 5 main methods to find extrasolar planets.