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Giant star is a dying water world

Artist's depiction of a comet swarm around the star CW Leonis
Artist's depiction of a comet swarm around the star CW Leonis  


By Richard Stenger
CNN

(CNN) -- A red giant star in its death throes seems to be vaporizing a horde of comets, raising the possibility that another planetary system possesses water, an ingredient necessary for known life, astronomers reported Wednesday.

The carbon-rich star was not expected to contain significant amounts of water. But an orbiting NASA radio observatory detected huge concentrations of water vapor around it.

"The most plausible explanation ... is that it is being vaporized from the surfaces of orbiting comets, dirty snowballs that are composed primarily of water ice," lead investigator Gary Melnick said Wednesday.

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Several hundred billion comets, located in the far reaches of the star system, would have been necessary to produce the intense concentration of water vapor, Melnick and his colleagues told reporters.

Although that amount seems colossal, the mass is comparable the estimated quantity of water in the Kuiper Belt, a swarm of icy debris beyond the orbit of Neptune, during the infancy of our solar system.

"Occasionally a comet comes in close to the sun and starts to vaporize," said team scientist Saavik Ford. But CW Leonis "is so much more luminous that the sun that comets start to vaporize even at the distance of the Kuiper Belt."

CW Leonis is about 500 light years from Earth, located in the constellation Leo. Astronomers think the red giant is shedding its outer material, which in tens of thousands of years will produce a nebula system.

"We think we are witnessing the type of apocalypse that will ultimately befall our own planetary system," said David Neufeld, who helped analyze the data from the Submillimeter Wave Astronomy Satellite, which has searched the universe for signs of water for more than two years.

In about six billion years or so, the sun will exhaust its hydrogen fuel supply and expand into a red giant like CW Leonis, incinerating planets along the way.

"Even Pluto will be vaporized, leaving a cinder of hot rock," Neufeld said.

The observations suggest that other planetary systems resemble our own, the astronomers said. More than 60 planets have been discovered outside the solar system, but their composition remains a mystery. The new findings boost speculation that many posses vast caches of water, like many bodies in our solar system.

Melnick, an astronomer at the Harvard-Smithsonian Center for Astrophysics, and his colleagues were to report their findings in the July 12 issue of the journal Nature.







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