A New Dwarf Planet Has Joined Our Solar System’s Family—Meet Pluto's 'Extreme Cousin'

Earth has a new neighbor that lives far, far away. Scientists from the Institute for Advanced Study's School of Natural Sciences believe they have found a new dwarf planet in extreme outer space.

Officially named 2017 OF201, the object is estimated to be about one-third the diameter of Pluto, making it large enough to be classified as a dwarf planet, the same designation given to Pluto in 2006.

According to the International Astronomical Union, to be considered a planet, an object must orbit a star, be mostly round, and be big enough that its gravity clears away any other objects of similar size near its orbit. Dwarf planets, like Pluto, can't clear their orbit of debris.

Sihao Cheng, an astrophysicist at the Institute for Advanced Study’s School of Natural Sciences who led the team that discovered the object, described it as an "extreme 'cousin' of Pluto."

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The new finding is known as a trans-Neptunian object, or TNO, which are bodies in the solar system that orbit the sun beyond Neptune, which is 30 times more distant from the sun than Earth. Because the object takes an incredibly lengthy 25,000 years to complete one orbit around the sun, it's only detectable at certain times.

Cheng discovered the object as part of an ongoing research project to identify TNOs and possible new planets in the outer solar system. The area beyond the Kuiper Belt, where the object is located, has previously been thought to be empty, but the team’s discovery suggests otherwise. 

"2017 OF201 spends only 1 percent of its orbital time close enough to us to be detectable. The presence of this single object suggests there could be another hundred or so other objects with similar orbits and sizes; they are just too far away to be detectable now," Cheng said.

He added: "Even though advances in telescopes have enabled us to explore distant parts of the universe, there is still a great deal to discover about our own solar system."