51 Pegasi. Coloured optical image of the star 51 Pegasi, a Sun-like star some 42 light years from Earth. In 1995 Michel Mayor and Didier Queloz of Geneva University, Italy, discovered that it was orbited by at least one planet. The planet was discovered by monitoring the light from the star. A change (doppler shift) in the frequency of the light revealed that the star was orbiting around a centre of gravity between it and a planet. This planet, 51 Pegasi B, is estimated to be about half as massive as Jupiter, and orbits only 7 million kilometres from the star, equivalent to 1/6th of Mercury's orbit around the Sun. Photographed using a charge-coupled device (CCD).