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Found: new dwarf planet on an incredibly wide orbit around the Sun

Alex Parker OSSOS team

A new dwarf planet has been found lurking in the Kuiper Belt — the large cloud of icy bodies that orbits at the fringes of the Solar System. The object, named 2015 RR245, was spotted by a team of international astronomers in February of this year, after looking over data from the Canada-France-Hawaii Telescope. The discovery was made as part of the Outer Solar System Origins Survey, an ongoing observation looking for objects beyond Neptune.

The researchers aren’t exactly sure how big 2015 RR245 is, but they estimate it to be about 435 miles wide. If so, that would make it the 18th largest object in the belt. But to be certain of its size, the astronomers need to measure the dwarf planet’s surface properties in more detail. "It's either small and shiny, or large and dull," Michele Bannister of the University of Victoria in British Columbia and a postdoctoral fellow with the OSSOS, said in a statement.

The new dwarf planet also has an incredibly wide orbit

The new dwarf planet also has an incredibly wide orbit that takes it much farther out than Pluto and takes 700 years to complete. At its closest approach to the Sun, the object comes within 34 astronomical units (aus) to our star — or 34 times the distance from Earth to the Sun. At its farthest, 2015 RR245 reaches a distance of 120 aus, or about three times the distance from Pluto to the Sun. Right now, 2015 RR245 is traveling closer to the Sun on its orbit, and will reach its closest approach in 2096.

This is the first dwarf planet discovered through OSSOS, though the survey has spotted hundreds of Kuiper Belt objects since it was launched in 2013. Dwarf planets are usually much larger than asteroids and other Kuiper Belt objects but too small to be considered planets. The International Astronomical Union defines a dwarf planet as an object orbiting the Sun that is big enough to be rounded out by its own gravitational pull. However, dwarf planets have not cleared out the "neighborhood around their orbit," meaning there are often other objects that cross their paths.

So far, only five dwarf planets have been recognized by the IAU — four in the Kuiper Belt and one in the Asteroid Belt called Ceres.

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