Sister solar system

Could San Francisco State astronomers have discovered the first signs that we are not unique?


Chris Colin
April 21, 1999 8:00PM (UTC)

For years, people have looked into the night sky and asked, "Are we alone?" and for years astronomers have been able to shrug: "That's what it looks like to us." After all, despite reputed crash landings of little green men in the New Mexico desert, no scientist had discovered a solar system that had the components that might allow Earthlike life to evolve.

But last Thursday, on a campus not known for its groundbreaking research, all that changed. As researchers around the world scrambled to revise their maps, San Francisco State University's R. Paul Butler and Geoffrey Marcy announced that they had determined that the star Upsilon Andromedae is host to a three-planet orbit, marking the first multiplanet system besides our own to be discovered. Until this point, it was believed that our system was unique in its capacity to support multiple planets.

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Butler and Marcy discovered the first of the three planets in 1996, using a relatively low-tech method that measures the movements of faraway planets. After this finding, the two teamed up with a handful of other astronomers to measure a minute series of "wobblings" observed in Upsilon Andromedae. Three years later, these wobblings have proven to be the consequence of competing gravitational
pulls, evidently exerted by two additional planets.

While it's too soon to chart the repercussions of this discovery, it's fair to surmise that it will have a significant influence on new directions in astronomy. Much of our understanding of planetary systems has emanated from the now-defunct theory that extrasolar systems with sunlike stars necessarily contained only one planet.

This finding also upsets the most basic theories of planetary formation. The three planets in this new solar system appear to be huge -- roughly 375 times the size of Earth -- yet they still orbit close to their star. In the past, astronomers believed that planets of this size could only develop far from the central star, where the cold would allow massive gaseous masses to accumulate.

While astronomers struggle with suddenly inadequate planet-formation theories, the rest of the world wants to know about aliens. With the surprise discovery of a solar system similar to ours comes a humble reckoning with
years of cosmological narcissism: We might not be so extraordinary after all. And this is just the kind of development groups like the SETI Institute (Search for Extraterrestrial Intelligence) appreciate.

"Clearly, we like the idea of a commonplace solar system," SETI astronomer Seth Shoftak said. "This is good news for alienkind."

While Shoftak echoed much of the optimism now circulating among UFO watchers, he gently pointed out that SETI has always been optimistic. Long before Upsilon Andromedae, the 15-year-old organization knew the odds.

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"At the lower limit, 3 to 4 percent of all stars have planets,"
Shoftak said. "With hundreds of billions of planets in our galaxy, and hundreds of billions of galaxies, that's a lot of real estate."

Upsilon Andromedae real estate isn't entirely new to SETI. In 1998 the organization aimed a 140-foot radio telescope at the planetary system and tuned in. "The occupants have so far remained coy," Shoptak said.


Chris Colin

Chris Colin is the author most recently of "Blindsight," published by the Atavist.

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