If a group of US astronomers is right, about two million years from now our solar system could be graced by the brightest comet ever.

The potential comet is a dwarf planet in the Kuiper belt, designated 2003 EL61. Astronomers at Caltech have plotted its likely path, and have found that a close encounter with Neptune could disturb its path enough to send it tumbling into the inner solar system, where it would become a short period comet.

Caltech's Professor Mike Brown announced his predictions at the American Astronomical Society meeting in Seattle.

He explained that the planetoid is very unusual, being mostly rock covered in a thin layer of ice. Objects in the Kuiper belt tend to have more ice than 2003 EL61, suggesting that it suffered a massive collision at some time in its history.

This could have knocked off most of its icy covering, and could explain its extremely fast rotation. The planetoid spins so quickly - a full rotation once every four hours - that it is rugby-ball shaped rather than near-spherical.

Professor Brown also speculated that after the encounter that spun 2003 EL61, some of the icy mantle could have reformed into smaller satellites. Some of these, he says, could already have made their way into the inner solar system. ®

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