Imagine an icy world so distant it takes over 24,000 years to orbit the sun once. That’s 2017 OF201, a newly spotted object beyond Pluto that scientists believe may qualify as a dwarf planet. But its unusual orbit has also raised questions about a popular theory involving a possible ninth planet in the outer reaches of our solar system.
Astronomers found 2017 OF201 by analyzing old telescope images taken between 2011 and 2018. They noticed a faint moving dot appearing in different parts of the sky. Based on its brightness and speed, scientists estimate it is about 700 kilometers in diameter, likely large enough for gravity to shape it into a sphere, a key feature of dwarf planets.
Unlike the neat orbit of planets like our Earth, 2017 OF201 follows a stretched path. It swings as close as 7 billion kilometers from the sun and as far as 245 billion kilometers.
2017 OF201’s strange orbit challenges the Planet Nine hypothesis, which was proposed in 2016 by Caltech astronomers Michael Brown and Konstantin Batygin. The idea suggests a massive, unseen planet – possibly a super-Earth – shapes the orbits of extreme trans-Neptunian objects (TNOs), causing them to cluster in space. However, astronomer Jiaxuan Li noted that 2017 OF201 deviates significantly from the orbital alignments of most extreme TNOs.
Study leader Sihao Cheng of the Institute for Advanced Study in Princeton added that this object is only visible during 1% of its long orbit and that many more like it could be out there – just too far to detect. He said that even with powerful telescopes, we still have much to explore in our own solar system.