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Distant stars that gobble up Earth-like planets are unlikely to be good hosts for life – after all, no one wants to share the neighbourhood with a world-devouring sun. Now astronomers have figured out how to identify the grizzly leftovers of a sun-like star's planetary feasting, which should make it easier to rule out planet-eaters and instead track down systems that still have habitable worlds.

Stars are mostly made up of hydrogen and helium, the fuel for nuclear fusion reactions that produce their heat and light. But they also can contain a spattering of other elements on their surfaces. Analysing starlight lets astronomers determine which elements are present in a star system, and gives clues to the kind of planets it contains.

To find out more, Keivan Stassun at Vanderbilt University in Nashville, Tennessee, and his colleagues used telescopes at the Las Campanas Observatory in Chile to look at a system containing a pair of sun-like stars called HD 20781 and HD 20782. The two stars formed from the same cloud of dust and gas, meaning they would initially have had the same chemical composition. Any differences must be down to their orbiting planets. Currently, we only see that one star has two Neptune-mass worlds and the other has a Jupiter-like planet.

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