Strange new object found at edge of Solar System

A large object has been found beyond Pluto travelling in an orbit tilted by 47 degrees to most other bodies in the solar system. Astronomers are at a loss to explain why the object's orbit is so off-kilter while being almost circular.

Researchers led by Lynne Allen at the University of British Columbia in , , first spotted the object in observations made with the Canada-France-Hawaii Telescope in December 2004. Since October 2005, they have made follow-up observations that have revealed the object's perplexing path.

Tentatively named 2004 XR190, the object appears to have a diameter of between 500 and 1000 kilometres, making it somewhere between a fifth and nearly half as wide as Pluto. It lies in a vast ring of icy bodies beyond Neptune called the Kuiper Belt, most of which orbit in nearly the same plane as Earth.

But at 47 degrees, 2004 XR190's orbit is one of the most tilted, or inclined, Kuiper Belt Objects known. That suggests it was flung out of the solar system's main disc after a close encounter with another object - such as Neptune or perhaps a star that passed by the Sun billions of years ago.

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