Astronomers have discovered a new dwarf planet, named 2017 OF201, far beyond Pluto’s orbit. It takes 25,000 years to orbit the sun—much longer than Pluto’s 248 years. This makes it one of the most distant objects ever found in our solar system, over 1,600 times farther from the sun than Earth at its farthest point. The discovery could change our understanding of the outer solar system and what lies beyond it.
The discovery was announced on May 21, 2025, by the International Astronomical Union. It came from a team led by Sihao Cheng of Princeton University. They were searching for the mysterious “Planet 9” and used data from large telescopes in Chile and Hawaii. Advanced computer tools helped them track a moving bright spot in the sky, leading to the identification of 2017 OF201.
This dwarf planet is about 435 miles wide, close in size to Pluto. But its orbit is unusual—long, stretched, and unlike most other known objects in the outer solar system. Scientists think it may have been flung into this orbit by a giant planet like Neptune or Jupiter. Others believe it may have come from the Oort Cloud, a distant shell of icy bodies surrounding the solar system.
The discovery also suggests that the Oort Cloud might be filled with many more hidden objects. Cheng believes there could be hundreds of similar dwarf planets waiting to be discovered. NASA’s New Horizons spacecraft is moving past Pluto but hasn’t reached these distant areas yet. This means there are still many mysteries to uncover.
Finally, the strange orbit of 2017 OF201 brings new doubt about Planet 9. While some scientists once believed in its strong effect on distant space objects, this new find suggests other explanations are possible. By studying 2017 OF201, researchers hope to learn more about the birth and history of our solar system. The full study is available on the arXiv research website.