Just when it appeared we had a firm understanding of the known realms within our solar system, astronomers have detected a new celestial entity that might alter our perception of the outer solar system.

The recently identified object, provisionally named 2017 OF201, is a frozen, remote world that might be a distant cousin of Pluto — and the term “distant” is no exaggeration. At its furthest point, this icy entity is more than 1,600 times farther from the sun than Earth is. Even at its nearest approach, it remains 44.5 times farther away from our home planet.

What distinguishes 2017 OF201 is its highly elongated orbit around the sun, which takes an astonishing 25,000 Earth years to finish. In comparison, Pluto circles the sun in only 248 years.

The origin of this enigmatic object is still uncertain. Researchers theorize it could have been ejected into its current orbit due to gravitational interactions with a massive planet such as Jupiter or Neptune. Another theory posits that it may have previously existed in the hypothetical Oort Cloud — a distant shell of icy remnants from the early solar system — before migrating back inward. The Oort Cloud has yet to be confirmed, as its far-off and faint objects are nearly impossible to observe directly.

The detection of 2017 OF201 was officially revealed on May 21 by the International Astronomical Union’s Minor Planet Center, which monitors small celestial bodies. Measuring roughly 435 miles (700 kilometers) in diameter, the object could potentially be classified as a dwarf planet — similar to the designation Pluto received after its reclassification in 2006.

“Although advancements in telescopes have allowed us to investigate far-off regions of the universe,” stated Sihao Cheng, a researcher at the Institute for Advanced Study who spearheaded the discovery, “there is still much left to uncover about our own solar system.”

Cheng and a group of graduate students from Princeton University discovered 2017 OF201 while seeking the elusive “Planet 9” — a theoretical massive planet thought to be affecting the orbits of far-off objects in the solar system. By employing computer algorithms, the team scrutinized years of archived images from the Victor M. Blanco Telescope in Chile as well as the Canada-France-Hawaii Telescope. By tracking faint, slow-moving points of light in the sky, they successfully identified this new entity.

Interestingly, 2017 OF201 does not exhibit the same orbital clustering pattern characteristic of other trans-Neptunian objects, prompting some scientists to reconsider the very existence of Planet 9.

“The presence of 2017 OF201 could indicate that Planet 9 or X may not exist,” remarked Jiaxuan Li, a co-author of the study, on his personal website. Their results are currently accessible on the arXiv preprint server.

This discovery also casts doubt on long-held beliefs regarding the outer regions of our solar system. The area beyond the Kuiper Belt — where 2017 OF201 is located — was once assumed to be mostly vacant. Yet NASA’s New Horizons spacecraft, which made headlines by flying past Pluto in 2015, has since ventured far beyond that distance and still has not reached the edge of the Kuiper Belt.

In 2019, New Horizons captured images of Arrokoth, a red, icy, dumbbell-shaped entity — the most distant object ever inspected by a spacecraft. Nonetheless, even that achievement implies there may be countless other far-off bodies waiting to be found.

If 2017 OF201 is only visible during the fleeting 1 percent of its orbit when it is relatively near Earth, it may suggest a vast population of similar objects hidden in the distant expanses of the solar system.

“The existence of this single object indicates there could be another hundred or so other entities with similar orbits and sizes,” Cheng noted. “They are simply too far away to detect at present.”

As our instruments and methodologies advance, this discovery serves as a reminder: the solar system is still filled with enigmas.