Marcy, Geoffrey W.

▪ 2001

      One day in 1983, American astronomer Geoffrey Marcy announced to colleagues that he planned to search for planets in other solar systems. His fellow astronomers thought him foolish to spend time on what they considered a futile pursuit. No one was sure such planets existed, and even if they did, scientists had no instruments with which to see them. Marcy was undaunted, however, and by 2000 he and his research team at San Francisco State University had detected 19 planets orbiting stars other than the Sun—nearly two-thirds of the total number of “extrasolar” planets hitherto discovered.

      Marcy was born on Sept. 29, 1954, in St. Clair Shores, Mich., and grew up in southern California. His parents bought him a telescope when he was 14, and, according to his mother, it “vanished into his room immediately.” In 1982 he earned a Ph.D. in astronomy and astrophysics from the University of California, Santa Cruz. From 1982 to 1984 Marcy was a Carnegie fellow at the Carnegie Institution of Washington, D.C. After deciding to devote himself to his search for extrasolar planets, he moved on to a professorship at San Francisco State, where he recruited a graduate student, Paul Butler, to help him develop instrumentation that would be sensitive enough to indicate the presence of such faraway objects. Marcy realized that no telescope would be powerful enough to see such a planet directly, but he thought that a large planet might exert enough gravitational force on its star that the star would move slightly, a motion that Marcy called a “wobble.” This motion, he predicted, would reveal itself as a slight shift in the wavelengths of light traveling from the star to the Earth. Eventually Marcy and Butler developed a light analyzer that could detect these shifts.

      Using this technique, two Swiss scientists, Michel Mayor and Didier Queloz, in 1995 became the first astronomers to detect a planet circling a star outside the Earth's solar system. Marcy confirmed their discovery, and the following year he and Butler discovered two more extrasolar planets. A succession of similar discoveries followed. In 1999 Marcy found a star with a wobble that suggested a huge planet would pass directly in front of the star and thereby block some of the star's light, and on November 7 of that year one of his colleagues noted a 1.7% decline in the brightness of the star at exactly the time Marcy had predicted. As a reward for his groundbreaking research, Marcy was appointed a professor of astronomy at the University of California, Berkeley, and accepted an invitation to head the university's proposed Center for Integrative Planetary Studies. In addition, in April 2000 he was named California Scientist of the Year.

David R. Calhoun

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