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Planets outside the solar system

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GALACTIC SURPRISE: A dust ring, in red, surrounds the star Fomalhaut, located at the centre of the image but is not visible.
GALACTIC SURPRISE: A dust ring, in red, surrounds the star Fomalhaut, located at the centre of the image but is not visible.

Dennis Overbye

A little more of the universe has been pried out of the shadows. Two groups of astronomers have taken the first pictures of what are most likely planets going around other stars.

The achievement, the result of years of effort on improved observational techniques and better data analysis, presages more such discoveries, the experts said, and will open the door to new investigations and discoveries of what planets are and how they came to be formed.

“It’s the tip of iceberg,” said Christian Marois of the Herzberg Institute of Astrophysics. “Now that we know they are there, there is going to be an explosion.”

Mr. Marois is the leader of a team that recorded three planets circling a star known as HR 8799 that is 130 light-years away in the constellation Pegasus. The other team, led by Paul Kalas of the University of California, Berkeley, found a planet orbiting the star Fomalhaut, 25 light-years from earth, in the constellation Piscis Austrinus.

In scratchy telescope pictures released on Thursday in Science Express, the online version of the journal Science, the planets appear as fuzzy dots that move slightly around their star from exposure to exposure. Astronomers who have seen the images agreed these looked like the real thing.

“I think Kepler himself would recognise these as planets orbiting a star following his laws of orbital motion,” Mark S. Marley of the Ames Research Centre in Mountain View said.

More than 300 so-called extrasolar planets have been found circling distant stars, making their discovery the hottest and fastest growing field in astronomy. But the observations have been made mostly indirectly, by dips in starlight as planets cross in front of their home star or by wobbles they induce.

Astronomers being astronomers, they want to actually see these worlds, but a few recent claims of direct observations have been clouded by debates about whether the bodies were really planets or failed stars. “Every extrasolar planet detected so far has been a wobble on a graph,” said Bruce Macintosh, astrophysicist from the Lawrence Livermore National Lab.

The new planetary systems are anchored by young bright stars more massive than our own sun and swaddled in large discs of dust, the raw material of worlds. The three planets orbiting HR 8799 are roughly 10, nine and six times the mass of Jupiter, and orbit their star in periods of 450, 180 and 100 years respectively, all counterclockwise.

Fomalhaut is about three times as massive as Jupiter, according to Mr. Kalas’ calculations, and is on the inner edge of a huge band of dust, taking roughly 872 years to complete a revolution of its star. — New York Times News Service

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