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First photos of planets outside solar system

A Canadian-led team of astronomers has captured images of three giant planets outside our solar system, orbiting a distant star known as HR8799.

The research team, led by astronomer Christian Marois of the National Research Council Canada/Herzberg Institute of Astrophysics, used advanced instrumentation and image-processing techniques known as exoplanet imaging to detect the three faint planets against the bright glare of their host star.

The primary star, barely visible to the naked eye, lies 130 light years from Earth in the constellation Pegasus. Its mass is about 1.5 times that of the sun and its age is about 60 million years, significantly less than the sun.

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The images were captured by the Gemini North and Keck telescopes at the Mauna Kea Observatories in Hawaii.

David Lafreniere, a postdoctoral fellow at the University of Toronto and member of the discovery team, said the pioneering work of Mr. Marois and colleagues in exoplanet imaging over the last couple of years has finally paid off.

"This is truly an amazing discovery," he said.

"Surely, astronomers from all around the world will be very busy over the next few years to figure out the most intricate details of this fascinating system."

Bruce Macintosh, a scientist at the Lawrence Livermore National Laboratory in California and a project collaborator, added: "It's amazing to have a picture showing not one but three planets."

"The discovery of the HR 8799 system is a crucial step on the road to the ultimate imaging of another Earth." He called it "a step on that road to understand if there are other planets like Earth and potentially life out there."

More than 200 planets in other solar systems have been detected in the last decade through indirect studies of their gravitational tug on their parent star. This indirect technique only measures the mass and orbit of the planet.

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Direct imaging offers many more possibilities of study, including the ability to detect planets at wider separations from their stars - as was in the case of this study.

"By making an image that shows the planet directly, we can study its properties in detail, measure its temperature and composition and try to understand its atmospheric structure," said Mr. Macintosh.

Infrared observations by satellites have shown evidence of a massive disk of cold dust orbiting the star.

Ben Zuckerman, a University of California Los Angeles professor of physics and astronomy and a co-author of the paper, has been studying dust disks orbiting nearby stars for decades. A similar dust disk exists in our solar system, produced by dust from the comets of the Kuiper Belt located just beyond the orbit of Neptune.

"HR8799's dust disk stands out as one of the most massive in orbit around any star within 300 light years of Earth," said Mr. Zuckerman.

Comparisons of images obtained in different years show the three planets, each roughly 10 times the mass of Jupiter, are all moving with and orbiting around the star, proving they are associated with it and are part of a solar system.

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In some ways, the HR8799 planetary system seems to be a scaled-up version of our solar system, with more massive planets in orbit around a larger and brighter star. These giant planets orbit relatively far away from their star, at roughly 25, 40 and 70 times the distance between the Earth and the sun.

The other Canadian on the team, which also included U.S. and British astronomers, was Rene Doyon of the Departement de Physique and Observatoire du Mont Megantic, Universite de Montreal.

The findings were published online Thursday by Science, an international weekly science journal.

Separately, a U.S. team using the Hubble Space Telescope discovered another planet orbiting a star in another constellation.

The planet discovered by Hubble is one of the smallest exoplanets found yet.

It's somewhere between the size of Neptune and three times bigger than Jupiter. And it may have a Saturn-like ring.

It circles the star Fomalhaut in the constellation Piscis Austrinus.

With a report from The Associated Press.

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