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Watery Star

November 9, 2010

The star known as CW Leonis is in hot water. No, it’s not in trouble -- it’s surrounded by hot water vapor. And it appears that the water is created by energy from other stars.

CW Leonis is about 500 light-years away. It’s nearing the end of its life, so it’s puffed up like a giant red balloon. It’s so big, in fact, that if it took the Sun’s place in our solar system it would extend beyond the orbit of Mars.

Even so, it’s barely visible to optical telescopes because it’s surrounded by clouds of soot -- molecules that are rich in carbon. The star forged the carbon in its core, then dredged it to the surface.

The star heats the sooty clouds, causing them to glow brightly in the infrared. In fact, at some wavelengths, CW Leonis is the brightest star in the entire infrared sky.

Infrared telescopes detected the chemical signature of water from the star. Early ideas said the water probably came from icy comets.

But the orbiting Herschel telescope found that the water is quite hot, which means it’s quite close to the star. At such close range, there’s no way it could have been supplied by comets.

Instead, Herschel astronomers say the ultraviolet energy from other stars has reacted with the material in the clouds to produce the water -- adding steam to the soot that encircles this odd star.

CW Leonis is not far from Regulus, the brightest star of Leo, which climbs into good view around 2 a.m. and stands high in the sky at first light.


Script by Damond Benningfield, Copyright 2010


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