The first planet, found orbiting 51 Peg
In October 1995 Michel Mayor and Didier Queloz of Geneva Observatory in Switzerland reported finding the first planet. Observing the star 51 Pegasi in the constellation Pegasus, they noticed a telltale wobble, a cyclical shifting of its light toward the blue and red ends of the spectrum. The timing of this Doppler shift suggests that the star wobbles because of a closely orbiting planet.

Since that time, astronomers from all over the world (U.S., Australia, Switzerland, etc) have discovered planets around 76 stars! The number of planets is ever greater because many of the stars show more than one planet, some even have three planets. A current list, updated every few weeks with new discoveries, can be found HERE.

What kind of planets are being found?
MASSIVE planets only. The planet masses quoted in the table to the right are in terms of Jupiter masses, M_JUP, which is 318x Earth, or 1/1000x the mass of the Sun.

Why are only massive planets found?
Massive planets create the greatest `wobble' in the star. We can not directly see the planet! Instead, we must depend on watching for the star `hosting' the planet to make a cyclic wobble motion due to the gravitational tug of the planet.

How do we detect wobbling Stars? ---The Doppler Technique.
We study the light coming from the star very carefully, and look for changes in the wavelength of the light, first to red, then to blue and back to red, in a continuous cycle. These changes represent motion of the star towards and away from us, as it orbits the planet-star center of mass.