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The Star That Ate a Mars

Astronomers study white dwarf pollution for clues to extrasolar planet ingredients


For several years, UCLA astronomers have studied GD 362, a peculiarly dirty white dwarf star 165 light-years away in the constellation Hercules. Now they are pretty sure why the atmosphere of this dense, hot but slowly cooling ghost of a once much larger star is so polluted. It ate a planet.

“We probably have a destroyed world here,” says Michael Jura, coleader of the UCLA team. Apparently a planet with the mass of Mars — a billion trillion metric tons or so of rock, iron, dissociated water and other ingredients — was dismembered and atomized, its remains now bobbing in the thin but dense, 10,000 kelvins atmosphere that GD 362’s powerful gravity holds close around itself.

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