spaceSpace and Physics

We May Just Have Found A New Dwarf Planet In Our Solar System


Jonathan O'Callaghan

Senior Staff Writer


This is a stock image but the discovery is likely red and round like this too. Dotted Yeti/Shutterstock

Astronomers think they might have found a new dwarf planet beyond the orbit of Neptune. It's about a quarter of the size of Pluto and may be one of thousands of objects awaiting discovery at the edge of our Solar System.

Tentatively named 2010 JO179, it was found using the Pan-STARRS Outer Solar System Survey by a team led by Matthew Holman from the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts. A paper describing the findings is available on arXiv.


From measuring the brightness of the object, the team believes it's about 600 to 900 kilometers (370 to 560 miles) across. For scale, Pluto is 2,370 kilometers (1,473 miles) wide.

The potential dwarf planet is located at a distance of 78.3 AU (astronomical units – 1 AU is the Earth-Sun distance), beyond the Kuiper Belt. There's an extremely small margin of error in this estimation. It is known as a trans-Neptunian object (TNO). For comparison, Neptune is 30.5 AU on average and Pluto is 39.5 AU.

The object in question appears red, which may be a common trait of the outer Solar System. MU69, a much smaller object in the Kuiper Belt that the New Horizons probe is rapidly bearing down on, is a similar color.

The intriguing 2010 JO179 is thought to be roughly round, completing a rotation once every 30.6 hours. Interestingly, it’s also in a 21:5 resonance with Neptune.


The team noted that it hadn’t been discovered before because it orbits at quite a high angle (30 degrees) to the rest of the Milky Way, and was therefore just outside the region of other searches, despite being quite bright.

This dwarf planet would be almost two times further from the Sun than Pluto. NASA

The discovery is particularly important because it hints that there are a lot more objects in this region, particularly in a similar resonance with Neptune. The researchers estimate that there are more than 6,700 such objects measuring more than 100 kilometers (60 miles) in diameter.

“2010 JO179 is a relatively nearby example of what is now being recognized as a very substantial population,” the researchers wrote in their paper.

While this object likely formed in its current position in the early Solar System, the team aren't discounting the idea that it was captured into its current orbit.


It is not the only dwarf planet we’ve found in the outer Solar System of late. Just last year, two objects called 2015 RR245 and 2014 UZ224 were found beyond Neptune. And astronomers are still earnestly trying to find the much larger Planet Nine in this region.

TNOs like this are thought to be leftover planetesimals from the formation of the Solar System 4.6 billion years ago. Finding and studying them could give us more clues about our own beginnings.

spaceSpace and Physics
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  • solar system,

  • neptune,

  • kuiper belt,

  • dwarf planet