It's a question that's been asked as long as humans have looked skyward: What's out there?
The announcement Thursday that scientists at San Francisco State University had discovered a new solar system very much like our own might hold the answer. Someday.
"We scientists don't think about these things from day to day," said Debra Fischer, a member of the SFSU team. "But long vision for us is that we hope to find Earth-like planets around other stars and find them in 'habitable zones,' which would mean that they may support life."
The San Franciscans, helped by astronomers from the Harvard-Smithsonian Center for Astrophysics and the National Center for Atmospheric Research, found strong evidence of three planets revolving around a star called Upsilon Andromedae. What that suggests is that the Milky Way teems with similar solar systems, increasing the likelihood of Earth-like planets capable of supporting life.
"We don�t spend our time 'out there,' thinking about this," Fischer said. "But I do believe the next generation of research will reveal -- in one to two decades -- Earth-like planets."
The Upsilon Andromedae solar system is the "first kin" to our own ever found, Fischer said. "It suggests that planets are formed much more easily than we originally imagined. And that the Milky Way, which has 200 billion stars, may be filled with other solar systems like this, and ours."
The first planet, and the closest orbiting Upsilon Andromedae, was discovered by SFSU astronomers R. Paul Butler and Geoffrey Marcy in 1996. This planet has three-quarters of the mass of Jupiter, and orbits 0.06 AUs (one AU equals the distance from the Earth to the Sun) from the star.
The middle planet is 0.83 AUs from the star and has at least twice the mass of Jupiter. The third planet has at least four times the mass of Jupiter, and is 2.5 AUs from Upsilon Andromedae.
No current theory suggested that so many giant planets would form around a star. Fischer said this suggested a new paradigm for planet formation. "There may be hundreds of small seed planets -- or planetesimals -- which grow in the disk of matter around a star," she said.
The planets that develop most quickly would then win the gravitational tug of war and remain in orbit around the star, weeding out the smaller planets.
Butler and Marcy felt that the velocity variations that revealed the closest planet to the star in 1996 were strange because they had an unusual amount of scatter. Earlier this year, enough data was gathered to confirm the second planet, which helped explain some of the confusing data.
But something else seemed to be tugging on the star, said Fischer. There was an extra wobble, which could only be explained by the presence of a third planet.
