Asteroids at distant star suggest planets

Vega, in northern night skies, has an asteroid belt much like our sun, a strong hint of yet-undiscovered planets orbiting other stars, U.S. astronomers say. The discovery makes it more similar to its twin, a star called Fomalhaut, than previously known and both are now known to have inner, warm asteroid belts and outer, comet-filled belts, similar in architecture to the asteroid and Kuiper belts in our own solar system, researchers at the University of Arizona said. Both belts in our solar system contain "planetesimals" -- leftover "crumbs" that didn't make it into planets, they said. "The wide gap between the two debris belts strongly suggests that multiple planets orbit these stars even though we can't see them," Kate Su, an astronomers at the university's Steward observatory, said. "We know this because in systems without planets, the debris material is evenly distributed." Gaps in debris disks are created by planets in a process called "sculpting," she said. "Planets scatter the objects under their gravitational influence. Over time, you won't see any dust or planetesimals in the region where they reside." "Overall, the large gap between the warm and the cold belts is a signpost that points to multiple planets likely orbiting around Vega and Fomalhaut," Su said.