Based on a University of Berkley press release
By observing the transit of a planet across the face of a distant star, astronomers prove that planets exist outside our solar system.
Last Friday, a team led by Greg Henry (Tenn. State) and Geoff Marcy (UC Berkeley) announced the discovery of a shadow of a planet crossing a distant star. Little known HD 209458, a Sun-like star 150 light-years away, had been suspected of harbouring planets from a slight wobble found in its motion. Henry et al. now find that this wobble exactly corresponds to a planet crossing the face of the star, creating the slight dimming effect of a partial eclipse. The astronomers were then able to make a groundbreaking estimate of the mass and radius of the extra-solar planet, which they find to have about two-thirds the mass of Jupiter but about 60 per cent larger radius.
“This is the first independent confirmation of a planet discovered through changes in a star’s radial velocity and demonstrates that our indirect evidence for planets really is due to planets,” said Geoffrey Marcy, a professor of astronomy at the University of California, Berkeley.