By Kathy Sawyer
Washington Post Staff Writer
Friday, April 16, 1999; Page A1

Elated astronomers yesterday announced the discovery of the first multi-planet system ever found around a normal star other than our own, moving civilization a step closer to its ancient quest for kindred havens where life might have arisen.

The signal of three orbiting worlds emerged from 11 years of telescope observations of the star Upsilon Andromedae, which is bright enough to see with the naked eye and is a relatively close 44 light years (about 264 trillion miles) from Earth in the constellation Andromeda. The findings were announced yesterday in San Francisco by two independent teams from four institutions who confirmed each other's conclusions using different equipment.

While the new solar system does not appear hospitable to life, the discovery "implies that planets can form more easily than we ever imagined, and that our Milky Way is teeming with planetary systems," said astronomer Debra Fischer of San Francisco State University, a member of one discovery team.

"This is the one we've all been waiting for," said Stephen Maran, a spokesman for the American Astronomical Society. "Astronomers' hearts are in their throats."

The discovery provides the "first clear evidence" that science fiction writers are right to depict their characters hopping from planet to planet throughout the galaxy, "like a bumble bee going from daisy to daisy," said Geoffrey Marcy, who led Fischer's team.

"We are witnessing, I think, the emergence of a new era of human exploration," Marcy said. The newfound solar system, following a trend set by the single planets detected around sunlike stars in recent years, exhibits orbital oddities and other unexpected properties that raise "profound questions" about where we fit in, he said, and whether our solar system may be "the result of some cosmic quirk of nature."

All three planets are whoppers, ranging from at least two-thirds to four times the mass of Jupiter – gravitational bullies that likely would have swept away any fledgling Earths. And the data suggest they are giant gas balls, like Jupiter, with no surface to pool liquid water – a requirement for life as we know it. Even if they have rather Earth-like moons, Marcy said in a phone interview, they are in zones where any water would either boil off or freeze.

Two of the planets orbit their star – which is younger and hotter than our sun – at distances similar to those of Venus and Mars (77 million and 232 million miles, respectively). These distances are not at all where conventional theory predicted such large planets would reside. The innermost of the triplets, first detected in 1996, skims so close to the star that its "year" – one complete trip around – takes only 4.6 days.

Upsilon Andromedae is currently "up" in the daytime and therefore not viewable. By June, as Earth travels in its orbit around the sun, the star will appear again in our night sky.

Earth's home galaxy, the Milky Way, contains some 200 billion stars. This is the first time anyone has detected more than one planet around any of them. (Scientists put in a different category the 1991 detection of planets around a whirling dead star in the constellation Virgo.) In fact, before this decade, astronomers had been frustrated in their attempts to find any extrasolar planets at all. But in a remarkable burst of discovery that began in 1995, planet hunters have detected a total of 20 worlds around sun-like stars (including the triplets).

Astronomers said yesterday's announcement should kill lingering suspicions that these bodies are not really planets, but dim, failed stars known as brown dwarfs. Alan Boss of the Carnegie Institution, formerly among the skeptics, said: "One of the key ways to be sure we've really got planets is to find a system of planets. . . . This is a major discovery."

The findings, which have been submitted to the Astrophysical Journal, raise questions as to "how this planetary system engendered three superplanets," said Robert Noyes, of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., a member of the second team, which included members from the High Altitude Observatory in Boulder, Colo. "This will shake up the theory of planet formation."

In 1996, Marcy and colleague R. Paul Butler, of the Anglo-Australian Observatory, had detected the innermost planet around Upsilon Andromedae, one of many lone planets they have found in surveys of hundreds of sunlike stars from the Lick Observatory in California and the powerful Keck telescope in Hawaii.

Technology is incapable of imaging conventional planets directly. Planet hunters use an indirect technique that measures a wobble induced in a star by the gravitational tugs of circling planets. More massive planets, and those orbiting most closely to stars, produce the strongest, most quickly readable signals.

But in the case of Upsilon Andromedae, the researchers noticed suspicious scatter patterns layered over the first wobble signature. By February, as they had hoped, they had accumulated enough observations to confirm the presence of a second planet there. But, Fischer said, "There was still too much extra noise" in the data.

Late one night in early March, Marcy recalled, he was at his computer plotting leftover noise when suddenly it took a familiar shape: another wobble. "The third planet popped right out of the screen." When Fischer first saw the signature, she said, "a chill went through me."

The second team, meanwhile, had been studying the star for more than four years using the Whipple Observatory in Arizona, and had exchanged data with Marcy. "Lo and behold," Marcy said, "the three-planet model fit their data too – like the shoe fit Cinderella." When he broke the news of the third world to Noyes, Marcy recalled, "I said, 'Bob, I hope you're sitting down.'‚"

The teams expressed relief and amazement at the remarkable agreement in their data. "This is such an extraordinary finding that you can't be absolutely sure of it unless you have independent confirmation," Noyes said. Even so, they conducted rigorous checks to eliminate all other explanations before going public.