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Planet hunters snap first pictures of other solar systems

The breakthrough images include a three-planet system around a sun-like star.

By Peter N. SpottsStaff Writer for The Christian Science Monitor / November 13, 2008

A dust ring, seen in red, surrounds the star Fomalhaut, that resides at the center of the image, and is not visible to the human eye in this image. The Hubble Telescope discovered the fuzzy image of the planet, known as Fomalhaut b, which is no more that a white speck in the lower right portion of the dust ring that surrounds the star.



In the hunt for solar systems beyond our own, astronomers have crossed an important threshold – capturing from the ground, as well as from space, the first direct images of planets around bright, sun-like stars.

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Since September, three teams say they have imaged planet-candidates. The most recent reports, published in Thursday’s issue of the journal Science, include a three-planet system around a variable star 128.5 light-years from Earth.

Until now, researchers have had to content themselves with shadowy, indirect approaches to finding planets – measuring a regular wobble in a star’s spectrum as gravity from its massive planets orbit and tug on it, or the cycle of brightening and dimming a star appears to experience as a planet crosses its face.

Over the past 20 years, such techniques have bagged more than 300 planets in solar systems in the Milky Way – some as distant as 17,000 light-years from Earth. Now, astronomers are beginning to spot the tiny specs of planets directly. What they can see, they can hope to follow up with more-detailed studies.

“This is the beginning of a new era,” says Ray Jayawardhana, an astronomer at the University of Toronto and a member of one of the three teams.

The approaches he and others use are detecting planets that the other techniques can’t, he explains. With three announcements in two months, “the floodgates are beginning to open. We’re learning about a whole new population of quite massive companions that are in fairly far-out orbits from their star.”

In many ways, the door to direct detection from the ground opened four years ago.

A team of astronomers led by Gael Chauvin, a researcher with the European Southern Observatory, found what appeared to be a giant companion to a brown dwarf – a dim star wannabe that never grew massive enough to ignite its fusion furnace.

The find still triggers some heated discussions. Is a brown dwarf really a star? If it isn’t, can you call its companion a planet?

In the end, it doesn’t matter, says Travis Barman, an astronomer at the Lowell Observatory in Flagstaff, Ariz. It represents a valuable anchor for one end of a spectrum of objects around which planet-like companions form.

Whatever the outcome of those discussions, the discoveries published this week represent what astronomer Mark Marley calls “compelling images” of companions “clearly orbiting stars.” Dr. Marley is a research scientist at the National Aeronautics and Space Administration’s Ames Research Center at Moffett Field, Calif.