What Have We Found?

In July 1995, two astronomers from the University of Geneva, Didier Queloz and Michael Mayor, found the first planet orbiting a normal star in the constellation of Pegasus by the spectroscopy method. The discovery of 51 Pegasus was confirmed by astronomers Geoff Marcy and Paul Butler of San Francisco State University. Marcy and Butler have since found numerous planets around other stars using the spectroscopy method. As of May 2000, we have found over 50 extrasolar planets. All of the planet-hunting methods tend to detect large planets -- about half the size of Jupiter to several times the size of Jupiter. These planets tend to orbit their parent stars within about 3 astronomical units (AU).

Photo courtesy NASA Some of the extrasolar planets found. The names of the planets are in the center of each row. The position of each planet in the row indicates its distance from its parent star in AU. The mass of the each planet is written to its right (MJ means "compared to the mass of Jupiter").

For the latest results, see The Search for Extrasolar Planets, Geoff Marcy's Web site at San Francisco State University.

Importance of Jupiter In our solar system, Jupiter plays an important role in clearing the inner solar system of passing debris. As many comets and asteroids pass from the outer solar system into the inner solar system, Jupiter's gravity breaks them apart. If Jupiter were not located where it is in our solar system, and were not so massive, more comets and asteroids would have collided with Earth, causing mass extinctions like that of the dinosaurs.