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New minor planet found in the distant solar system
On May 21, 2025, the International Astronomical Union’s Minor Planet Center added a new object to their list: 2017 OF201. This is likely the largest new object found in our solar system since the minor planet 2014 UZ224, which the IAU recognized in 2016. Astronomers found the new object in old images and has a diameter somewhere between 290 and 510 miles (470 and 820 kilometers) across. At its closest, 2017 OF201 comes within 45 astronomical units (1 AU equals the Earth-sun distance) of the sun. At its farthest, it can extend as far as 1,629 AU from the sun. Currently, the new solar system body is about 90.6 AU distant.
This distance would make it a trans-Neptunian object. These objects orbit the sun at a distance greater than Neptune, which is 30 AU from the sun. There are many trans-Neptunian objects in our solar system. Pluto is one. So are Eris, Haumea, Makemake and more. In fact, there are some 3,000 known trans-Neptunian objects and about 900 of those have official numbered designations.
But 2017 OF201 gets so far from the sun that it also qualifies as an extreme trans-Neptunian object. These objects have their longest distance from the sun of at least 150–250 AU. So with a distance that extends more than 1,600 AU, 2017 OF201 certainly qualifies.
Is it Planet 9?
And, no, this is not a possible candidate for Planet 9. While 2017 OF201 is probably bigger than the dwarf planet Ceres in the asteroid belt, it’s not what astronomers have been looking for to solve the mystery of Planet 9. Any Planet 9 would have to be about 5 to 10 times the mass of Earth to explain the gravitational clustering of objects in the distant solar system.
For more on the thrilling search for Planet 9, watch EarthSky’s Dave Adalian’s interview with planet hunter Mike Brown.
Bottom line: The International Astronomical Union’s Minor Planet Center announced a new minor planet on May 21, 2025, which is fairly large and has a huge, irregular orbit around the sun.
Via Minor Planet Center