Star's dust ring hints at alien planets

A ring of dust around a nearby star may owe its unusually tidy appearance to the possible presence of two planets sculpting the ring, U.S. researchers say. The dust ring around the star Fomalhaut, just 25 light-years away from Earth, is thin with sharply defined inner and outer edges, a shape astrophysicists say is unlikely unless something is shepherding the ring particles into line. "The best explanation so far is that there are two planets out there," astrophysicist Aaron Boley of the University of Florida told ScienceNews.org Boley and his colleagues used a collection of radio telescopes in the Chilean high desert to map the location of particles that are tugged around only by the gravity of planets and not by the radiation from a star. "We want to look at material that's only affected by the planet," Boley says. What they found was a dust a ring with well-defined edges, suggesting the presence of so-called shepherding bodies. "We do see a similar scenario in our solar system, with the Epsilon ring of Uranus being herded by two small moons," astrophysicist Ray Jayawardhana of the University of Toronto said. Planets, not moons, could be responsible for sculpting the Fomalhaut ring, researchers said, one cleaning up the inner edge and the other doing the same to the outer edge. The planets are each probably between the size of Mars and a super-Earth, they said, too small to be seen or detected with available technologies, "These sharp edges of the disk do indicate that there should be some planet in there that hasn't necessarily been seen yet," astronomer Markus Janson of Princeton University said.