Astronomers have identified a potential new dwarf planet, designated 2017 OF201, residing in the remote outer reaches of our solar system beyond Neptune. The discovery, announced on May 21, 2025, by the International Astronomical Union's Minor Planet Center, was led by Sihao Cheng from the Institute for Advanced Study, along with colleagues Jiaxuan Li and Eritas Yang from Princeton University.
Estimated to be approximately 700 kilometers (435 miles) in diameter, 2017 OF201 is potentially large enough to be classified as a dwarf planet. Its orbit is highly eccentric, taking around 25,000 years to complete a single revolution around the Sun. At its farthest point (aphelion), it is more than 1,600 times the Earth's orbital distance from the Sun, while at its closest (perihelion), it is 44.5 times the Earth's distance, similar to Pluto's orbit.
The unusual orbit of 2017 OF201, discovered using archival data from the Victor M. Blanco Telescope and the Canada-France-Hawaii Telescope, may challenge existing theories about Planet Nine. Unlike other extreme trans-Neptunian objects (ETNOs), its orbit doesn't cluster in the way that would support the Planet Nine hypothesis. This suggests that the gravitational influences shaping the outer solar system may be more complex than previously understood. Further observations are needed to determine its exact size and orbital characteristics, potentially reshaping our understanding of the outer solar system.