Scientists of the Outer Solar System Origins Survey (OSSOS) have discovered a new dwarf planet out in the far reaches of the Solar System, orbiting the Sun at nearly twice the distance as Neptune.
Designated 2015 RR245, this giant ball of ice lives in the icy region of space beyond Neptune’s orbit called the Kuiper Belt. The Kuiper Belt is home to many dwarf planets, including Pluto. 2015 RR245 is approximated to be 700 km wide, about twice as big as Sri Lanka. It also orbits the Sun over a period of a whopping 700 years, at a distance of 17 billion km from it. At that distance, it takes sunlight over sixteen hours to reach the dwarf planet (it takes Pluto nine).
RR245 was discovered by J.J. Kavelaars of the National Research Council of Canada in February of this year. He spotted the body while he was looking through images taken in September of 2015 by the Canada-France-Hawaii Telescope situated atop the Mauna Kea volcano in Hawaii. “There it was on the screen – this dot of light moving so slowly that it had to be at least twice as far as Neptune from the Sun,” said Michelle Bannister, a postdoctoral fellow with the survey at the University of Victoria, British Columbia, in a press release. While the team did not expect to find dwarf planets, this being their only discovery, they have discovered over 500 large bodies beyond Neptune in their quest to understand the outer Solar System. Kavelaars himself holds an impressive track record of discovering small objects beyond Jupiter, including new moons of Saturn and Uranus.
The discovery of RR245 should not come as a surprise at all. Astronomers guess that the Kuiper Belt is populated by hundreds of such bodies just waiting to be discovered. There are at least six other bodies that are a step away from being classified as dwarf planets and over 350 identified bodies that could fall under the same category sometime in the future.
The International Astronomical Union (IAU) has officially accepted RR245 as a dwarf planet as it satisfies the three necessary criteria: it orbits the Sun, it has enough gravity to hold itself together as a spheroid, but it hasn’t cleared its neighbourhood. Clearing one’s neighbourhood would mean that the body is the dominating gravitational force in its vicinity. This is the criteria that Pluto failed to fulfil, causing it to be demoted from a planet to a dwarf planet. Pluto’s nemesis, so to speak, was another dwarf planet named Eris whose discovery promptly led scientists to accept that there may be many Pluto-sized objects in the Kuiper Belt. With the addition of RR245 to the list, there are now six confirmed dwarf planets: five in the Kuiper Belt and one in the asteroid belt (between the orbits of Mars and Jupiter)
Once the precise size and orbital path of RR245 is determined, the IAU will name the body. As its discoverers, the OSSOS team members can submit their candidate names for the members of the IAU to vote on. RR245 is on a highly elliptical orbit that takes it far out, upto 29 billion km away from the Sun. It will make its closest approach to the star at 5 billion km in 2096.