November 14, 2008

Astronomers Capture Images Of Distant Solar System

Two teams of astronomers have captured the first images of a distant solar system that appears to be orbiting a star.

The images show three planets orbiting a star named HR8799, which is 140 light years away and about 1.5 times the size of our sun. The fourth gaseous planet orbits a separate star.

The three planets in orbit around HR8799 range in size from five to 13 times the mass of Jupiter and are probably only about 60 million years old. They decrease in size away from the parent star in similar fashion to our own solar system.

Christian Marois of the Herzberg Institute for Astrophysics, Canada, and his team used the Keck and Gemini telescopes in Hawaii to look near a star called HR 8799, which is just visible to the naked eye.

They used the infrared, high-contrast capabilities to help subtract the bright light from stars and focus in on light coming from the planets' heat or reflection.

Being able to directly detect the light from these planets will allow astronomers to study their composition and atmospheres in detail.

For more than a decade, scientists have discovered more than 300 planets outside our solar system, but they have done so indirectly, by measuring changes in gravity, speed or light around stars.

"Every extrasolar planet detected so far has been a wobble on a graph. These are the first pictures of an entire system," said Bruce Macintosh, an astrophysicist from Lawrence Livermore National Laboratory.

"We've been trying image planets for eight years with no luck and now we have pictures of three planets at once."

In 2004, astronomers came to the theory that the three-planet system existed, but were not able to produce an image of the system until now.

"But we finally have an actual image of an entire system," Macintosh said. "This is a milestone in the search and characterization of planetary systems around stars."

In some ways, this planetary system seems to be a scaled-up version of our solar system orbiting a larger and brighter star, Macintosh said.

The fact that each of the planets decrease in size with distance from the star leads scientists to believe the system was also formed through accretion.

Marois would not rule out the existence of other planets in the newly-discovered system.

"The detection of the three planets around HR 8799 does not mean that no planets are orbiting at smaller separations. Other gas giant or even rocky planets could reside there."

The current results will support theories of how planets form from the grand discs of dust and material around stars, and lead to better estimates of how many Earth-like planets are likely to exist.

Macintosh is now assembling a team to construct the Gemini Planet Imager - a more advanced optics system designed to block the light of bright stars and reveal even fainter planets.


Image 1: Near-infrared false-color image taken with the W.M. Keck II telescope and adaptive optics. The three planets are labelled b, c, and d. The colored speckles in the center are the remains of the bright light from their parent star after image processing.

Image 2: Artist's conception of the multiple planet system HR 8799, initially imaged by Gemini North adaptive optics and confirmed with W.M. Keck Observatory imaging. Gemini Observatory artwork by Lynette Cook


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