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Water seen in rubble around star

Debris was part of an asteroid that held the ingredients for habitable planets

PLANET BUILDER  The immense gravity of a white dwarf star, GD 61, shattered a water-laden asteroid (shown in an artist’s conception) into a cloud of debris.

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For the first time, astronomers have discovered the watery building blocks of Earthlike planets whirling around a star outside our solar system.

The star, GD 61, is a white dwarf: a dying star with a gravitational pull strong enough to suck in surrounding asteroids and planets. As GD 61 gobbles up orbiting bodies, it shreds them into a dusty cloud of rubble, says astronomer Jay Farihi of the University of Cambridge.

Using data from the Hubble Space Telescope, Farihi and colleagues analyzed the cloud’s ingredients. They found rock-forming elements such as iron and magnesium, but also a wealth of oxygen. Only one possibility can explain the oxygen, Farihi says: “It has to be water.”

The water and rocky material were part of a large asteroid before GD 61 ripped it to pieces, the researchers report in the Oct. 11 Science.

Just a few waterlogged asteroids smashing into a rocky planet could deliver enough water to fill oceans and lakes. The findings suggest that habitable planets may have once orbited GD 61, a star just 150 light-years away in the constellation Perseus.

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