SEATTLE -- The solar system may contain about 1,000 planets, not just the nine that are now known, according to a new theory presented yesterday by astronomer Alan Stern of the University of Colorado.
Untold numbers of Pluto-sized planets may have orbited among the known planets after the solar system's birth almost 5 billion years ago and now may circle so far away from the sun that they have yet to be detected, Stern told a meeting of the American Astronomical Society.
As startling as the new theory seems, some astronomers here found it a reasonable way of explaining some of the solar system's known enigmas. "I don't know why we didn't all think of it before," said Stephen Maran, spokesman for the society and an astronomer at NASA's Goddard Space Flight Center. "It's a startling new idea, but it's so obvious when you think of it."