Geoffrey W. Marcy, Professor of Astronomy at the University of California at Berkeley and Adjunct Professor of Physics and Astronomy at the San Francisco State University, was a pioneer in the discovery of planets outside the solar system. He and his colleagues found 70 of the first 100 extra-solar planets to be discovered. He confirmed Professor Michel Mayor's discovery of the first extra-solar planet and found the first multiple-planet system around a star, the first planets known as Saturn candidates, the first transiting planet, and co-discovered the first Neptune-sized planets. In recognition of his discoveries he and long-time collaborator Paul Butler were awarded the National Academy of Science's Henry Draper Medal. Professor Marcy also received the Nasa Exceptional Scientific Achievement Medal. Professor Mayor, of the Department of Astronomy at the University of Geneva and Director of the Geneva Observatory, discovered the first extra-solar planet, 51 Pegasi B, in 1995 at Haute Provence Observatory, France, together with Didier Queloz. He and his research team have since been involved in the discovery of many other such astronomic bodies. In August 1998 he was awarded the Swiss Marcel Benoist Prize in recognition of his work and its significance for human life. He was awarded the Balzan Prize in 2000 and the Einstein Medal in 2004. He has been president of several international scientific institutions. An extra-solar planet (or exoplanet) is a planet that orbits a star other than the Sun, and therefore belongs to another planetary system. Although their existence had long been considered a possibility, no planets orbiting main sequence stars were discovered until the 1990s. The discovery of extra-solar planets raises the question of whether they support life.