Oakland, Calif. A newly discovered pair of planets circling a distant star could be evidence that solar systems containing habitable planets like our own are common in the universe.
The two planets resemble Jupiter and Saturn in size and distance from their star, which is about 5,000 light years away from our own.
"One of the reasons we look for planets is to find out if we're not alone in the universe," said Kem Cook, an astrophysicist at Lawrence Livermore National Laboratory, where the method used to detect the new planets was first developed in the early 1990s.
The planet-hunting technique, known as gravitational microlensing, takes advantage of the way a star's gravity bends and focuses light from a brighter, more distant star.
For several weeks in the spring of 2006, 69 space scientists in 11 countries around the world watched as the stars aligned in a particularly bright microlensing event revealing the two new planets orbiting a star 5,000 light years away.
Their discovery bolsters a theory of how our own solar system formed.
The idea is that a cloud of gas and dust began to collapse in on itself. As gravity caused it to condense, it spun faster and faster, forming a disk. The hot center became the sun, and the rest of the matter clumped together into planets.
Jupiter, the largest gaseous planet, formed just far enough away from the sun for ice and gas to survive. The other gas giant, Saturn, formed from condensing ice and gas farther out. Only rocky matter survived closer to the sun and formed Earth, Mars, Venus and Mercury.
The newly discovered planets are slightly smaller than Jupiter and Saturn and are orbiting a smaller star, but they are proportionally the right distance away from their star to have been formed in a similar way, and likely receive the same amount of warmth from their star.
This opens the possibility that rocky planets exist closer to the star in the sweet spot where liquid water can exist and potentially give rise to life.
"There could be rocky planets closer in, but we couldn't actually detect them if they were there," Gaudi said. "There could be an earth analog."
Still, if our solar system and this distant system formed the same way, it could be a fairly common story in the universe which means habitable planets like ours could also be common.