Buffy the theory slayer?

[Swede]

2004 XR190, however, follows a nearly circular path. And it is too distant to have come into direct contact with Neptune, travelling between 52 and 62 AU from the Sun. Its orbit is also too circular - and too small - to have been tilted by a passing star, says Allen.

These traits make the object, nicknamed "Buffy" after the US television series about a vampire slayer, hard to explain. "Maybe Buffy is going to be a bit of a theory slayer," Allen told New Scientist.

But she suggests one theory that might account for the space rock's strange orbit. It involves a commonly held notion that early in the solar system, Neptune itself moved outward into its present orbit, from around Uranus's current location.



http://www.newscientist.com/article.ns?id=dn8455