Scientists spot planets orbiting a sunlike star
8/24/2010GENEVA - Scientists say they've found five, six, or maybe seven planets orbiting a sunlike star more than 100 light-years away.
It's the richest planetary system so far found and may contain at least one planet nearly as small as Earth - which would make it the smallest planet found outside the solar system.
One astronomer said it's part of a growing body of evidence that the universe is full of planets and that several of them could be similar to our own.
Although most of the planets identified are large - about 13 to 25 times the mass of Earth - those behind the discovery, announced Tuesday at a conference in France, say they're nearly certain they've identified one only 1.4 times the size of Earth.
Scientists have been spotting planets beyond our solar system for about 15 years and have now catalogued about 450.
Most finds have been limited to one or two or three planets, usually gargantuan balls of gas similar to Jupiter or Saturn. But at up to seven planets, the new find is almost as rich as our own solar system, which counts eight.
Christophe Lovis of Geneva University, one of the scientists behind the find, said the first five were most comparable to Neptune.
"They are made essentially of rocks and ice. They have a solid core. But on top of that is a layer of gas, hydrogen and helium most likely," he said. "They are probably not habitable."
The sixth is possibly a Saturn-like planet, and the seventh, the smallest, would be so close to its star that its "year" would take just over a day.
He and his team haven't been able to observe the planets directly, which is typical.
Few planets can be seen against the blazing light given off by their much more massive parent stars. The European Southern Observatory compares the challenge to "spotting a dim candle in front of a raging forest fire."
So the scientists used the observatory's 11.8-foot telescope at La Silla, Chile, to study the planets' parent star, known as HD 10180. Over six years, they took 190 measurements, checking the star for the telltale wobbling caused by the gravitational forces of nearby planets.
The find was made by researchers from Switzerland, France, Germany, and Portugal and has been submitted to the journal Astronomy and Astrophysics.