Introductory Astronomy: Extra Solar Planets

The first planets ever known outside our solar system were discovered in 1991 by Alexander Wolszczan of Penn State University. He discovered them using the Arecibo radio telescope. The planets Dr. Wolszczan discovered orbit around pulsars.

Since then, several more planets have been discovered around normal stars. Most of these planets are giants, like Jupiter. The first planet orbiting a solar-type star was 51 Pegasi , discovered by two Swiss astronomers, Machel Mayor and Didier Queloz. This planet has a mass equal to 0.6 times the mass of Jupiter, but orbits much closer to its star than our planet Mercury orbits the Sun!

Astronomers are interested in these planets for several reasons. These planets suggest that our solar system is not unique, that star formation often results in the formation of planets. The existence of these planets also suggests that we may one day find intelligent life on other worlds. After all, if planets can form around other suns, perhaps intelligent life forms can develop too!

To learn more about the other planets which have been discovered, click here.