2 Planets Found In Solar System That Is Similar To Our Own

By Marc Kaufman
Washington Post Staff Writer  
Friday, February 15, 2008

Researchers have discovered two planets in a solar system 5,000 light-years away that appears to be structured in significant ways like our own.

The planets are gas giants similar to but smaller than Jupiter and Saturn, and their relative sizes are also similar. In addition, they orbit their star at distances proportional to the distances of Jupiter and Saturn from the sun.

"This is the first time we've found a Jupiter-like planet in the same system as a Saturn planet," said Scott Gaudi of Ohio State University, lead investigator on the project. "There's reason now to believe there are probably many more solar systems like it."

The discovery, published online yesterday by the journal Science, lends support to the long-held belief of many astronomers that there are many planets orbiting their stars in configurations similar to that of our solar system. However, most of the more than 260 planets discovered were far closer to their suns than astronomers had theorized, and the planets were larger than expected.

Gaudi said that was most likely a result of the techniques used to search for the planets, techniques that work best at finding large planets that orbit close in. His group used a different method -- called gravitational microlensing -- that required collaboration with professional and amateur astronomers from around the world.

Using that technique, the two planets were discovered when the star they orbit crossed in front of a more distant star, as seen from Earth. For a two-week period from late March through early April of 2006, the nearer star magnified the light shining from the farther star by about 500 times.

Taking advantage of that magnification, astronomers were able to detect the planets as they appeared to cause their star to brighten slightly.

"This is a landmark discovery because it implies that solar system analogs may be very common, at least scaled-down versions," said Sara Seager, an extra-solar planet expert from the Massachusetts Institute of Technology. ". . . We are on an inexorable path to finding other Earths."

Seager said: "We are seeing the emergence of a new planet-finding technique -- one that opens up an entirely new capability for planet finding. It is more powerful than we ever thought possible."

This is the third time a Jupiter-mass planet has been found by microlensing, Gaudi explained. In the previous two cases, the presence of any additional planets would have been very difficult to detect.

"This is the first time we had a high-enough magnification event where we had significant sensitivity to a second planet -- and we found one," Gaudi said. "You could call it luck, but I think it might just mean that these systems are common throughout our galaxy."

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