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News Release 99-024

Astronomy Teams Find First Multi-Planet System, Other Than Our Own, Orbiting Star

April 15, 1999

This material is available primarily for archival purposes. Telephone numbers or other contact information may be out of date; please see current contact information at media contacts.

The first believed multiple planet system orbiting around a sun-like star has been found by independent teams of astronomers, including National Science Foundation (NSF)-supported researchers from San Francisco State University and from the Anglo-Australian Observatory.

In 1996 San Francisco State's Geoffrey Marcy and R. Paul Butler of the Anglo-Australian Observatory detected a near Jupiter-sized planet orbiting the star Upsilon Andromedae.

Recently, the scientists, after analyzing 11 years of telescopic observations at Lick Observatory near San Jose, Calif., picked up signals of what appears to be two additional planets within the same system based on newly gathered data. The new data indicates there are at least a trio of planets orbiting this star, making the Upsilon Andromedae grouping the first solar system ever found that mimics our own.

These newly discovered planets are more distant from its star than the one discovered three years earlier. The middle planet is estimated at twice the size of Jupiter, and the outermost planet, four times Jupiter's mass. Both orbit its star in elliptical patterns, as in previously known discoveries of extrasolar planets.

Meanwhile, a second team of astronomers from the Harvard Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., and from the NSF-supported High Altitude Observatory (HAO) in Boulder, Colo. found independent evidence of the two new planets using the Smithsonian's Whipple Observatory near Tuscon, Ariz.

Butler is the lead author of a paper that describes the trio of planets for the Astrophysical Journal. Contributing colleagues include Marcy, Debra Fischer of San Francisco State, Robert Noyes, Sylvain Korzennik, Peter Nisenson and Adam Contos, all of the CfA, and Timothy Brown of HAO.

"These planets are giants," James P. Wright, who heads special programs in astronomy for NSF's Division of Astronomical Sciences, said. "It's impressive that these results have been independently corroborated by these teams."


Editors: At San Francisco State University, media contact is: Blake Edgar, 415-338-6747,
At CfA, Harvard, media contact is: Megan Watzke, 617-495-7463,
At UCAR, media contact is: Anatta, 303-497-8604,
For images, see:

Media Contacts
William C. Noxon, NSF, (703) 292-8070, email:

Program Contacts
James P. Wright, NSF, (703) 292-8816, email:

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