Astronomers have found that a previously overlooked rocky body that lies in the Kuiper belt beyond Neptune is far larger than previously thought, making it the third largest dwarf planet in our solar system, after Pluto and Eris.

Previously thought to be a generic lump of space rock, (225088) 2007 OR10 doesn't have a proper name, although it's been nicknamed 'Snow White' in the years before it was thought to be anything more than a large, but not particularly interesting Kuiper Belt object.


The latest findings (pdf), published in The Astronomical Journal by András Pál and his team from Hungary's Konkoly Observatory, combine optical light curve data from Nasa's Kepler space telescope's K2 extended mission with thermal infrared data recorded by the Herschel Space Observatory.

In order to see this embed, you must give consent to Social Media cookies. Open my cookie preferences.

The combined data reveals that Snow White has a diameter of around 1,535 kilometres: far larger than its previously presumed diameter of 1,280 kilometres, making it the third largest dwarf planet so far discovered. It's around 100km larger than Makemake and about a third smaller than Pluto. The team also found that the dark dwarf planet has an unusually slow rotation, taking around 45 hours to complete a full day's spin. "Our revised larger size for 2007 OR10 makes it increasingly likely the planet is covered in volatile ices of methane, carbon monoxide and nitrogen, which would be easily lost to space by a smaller object," said Pál. "It's thrilling to tease out details like this about a distant, new world—especially since it has such an exceptionally dark and reddish surface for its size."

Brought to prominence by its new size and intriguing rotational characteristics, it seems likely the neglected dwarf planet will finally get a proper name. Discovered in 2007 by Meg Schwamb, Mike Brown and David Rabinowitz, the honour of naming it falls to them. "The names of Pluto-sized bodies each tell a story about the characteristics of their respective objects," said Schwamb. "In the past, we haven't known enough about 2007 OR10 to give it a name that would do it justice. I think we're coming to a point where we can give 2007 OR10 its rightful name."