Belt Tightening: Icy orbs are surprisingly small

Over the past few years, astronomers have reported large objects lurking in the Kuiper belt, a distant region of the solar system that seems to be a reservoir for comets. Some of the objects seemed to be half the size of Pluto. But observations now suggest that many are much smaller than previously estimated. If confirmed, the findings will force astronomers to drastically lower their estimate of the total mass of the realm of icy objects that orbit the sun beyond Neptune.

Objects in the Kuiper belt range from dust-grain size to more than 1,000 kilometers across. Pluto, at 2,400 km in diameter, is considered by many astronomers to be the largest member of the Kuiper belt.