New Dwarf Planet Discovered Beyond Pluto, Hinting At Hidden 'Planet X'

Astronomers have indeed discovered a potential new dwarf planet in the outer reaches of our solar system, far beyond Pluto. This object, named 2017 OF201, is estimated to be approximately 700 kilometres (435 miles) in diameter, which could qualify it as a dwarf planet. Its extreme orbit takes around 25,000 years to complete, with its closest point being 44.5 times the Earth's distance from the Sun and its farthest point being over 1,600 times the Earth's distance.

As per a news release, Cheng made the discovery alongside colleagues Jiaxuan Li and Eritas Yang from Princeton University, using advanced computational methods to identify the object's distinctive trajectory pattern in the sky. The new object was officially announced by the International Astronomical Union's Minor Planet Centre on May 21, 2025, and in an arXiv preprint shared on May 21.

According to astrophysicist Sihao Cheng of the Institute for Advanced Study in Princeton, New Jersey, "The object's aphelion-the farthest point on the orbit from the Sun-is more than 1600 times that of the Earth's orbit," explains Cheng. "Meanwhile, its perihelion-the closest point on its orbit to the Sun-is 44.5 times that of the Earth's orbit, similar to Pluto's orbit."

This extreme orbit, which takes the object approximately 25,000 years to complete, suggests a complex history of gravitational interactions. "It must have experienced close encounters with a giant planet, causing it to be ejected to a wide orbit," says Yang. "There may have been more than one step in its migration. It's possible that this object was first ejected to the Oort Cloud, the most distant region in our solar system, which is home to many comets, and then sent back," Cheng adds.

"Many extreme TNOs have orbits that appear to cluster in specific orientations, but 2017 OF201 deviates from this," says Li.