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Planets’ gravity tidies stellar ring

Dust disk around Fomalhaut hints at pair of orbiting bodies

3:32pm, April 6, 2012

Two small planets might be sculpting an enormous dust ring around the star Fomalhaut, a mere 25 light-years away from Earth.

But it’s not too likely that either planet is the notorious Fomalhaut b, which once held the title of the first directly imaged exo-world (SN: 12/6/08, p. 5).

New observations have revealed that the ring is thin, with sharp inner and outer edges — an unlikely shape, unless something is keeping the ring particles neatly in line.

“The best explanation so far is that there are two planets out there,” says astrophysicist Aaron Boley of the University of Florida, coauthor of a study to appear in Astrophysical Journal Letters.

Boley and his colleagues looked at the Fomalhaut system because they wanted to know how planets that are very, very far from their star might differ from planets that are snuggled closer in. Fomalhaut’s ring is more than 100 times

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