A team of scientists has discovered a strange, icy object at the outermost edge of the solar system that may be large enough to qualify as a dwarf planet, according to a recent study.
Named 2017 OF201, the object is roughly 435 miles (700 kilometers) wide and follows a highly eccentric orbit that takes it as far as 1,600 astronomical units (AU) from the sun—well beyond the Kuiper Belt, a distant region of icy bodies beyond Neptune.
The discovery was confirmed by the Minor Planet Centre of the International Astronomical Union, based on telescope data collected over the past seven years from observatories in Chile and Hawaii.
Astrophysicist Sihao Cheng of the Institute for Advanced Study in Princeton, who led the study, said 2017 OF201 may help reveal secrets of the solar system’s distant frontier, long thought to be mostly empty space.
“It is potentially large enough to qualify as a dwarf planet,” Cheng said, noting its wide and elongated orbit suggests a history of orbital migration likely influenced by a massive planet in the distant past.
While its exact composition is unknown, Cheng said it is “likely similar to other icy bodies” found in the Kuiper Belt.
Currently, 2017 OF201 is located 90.5 AU from the sun—meaning it is 90.5 times farther from the sun than Earth. For comparison, Pluto’s distance ranges between 30 and 49 AU.
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The object takes about 25,000 years to complete one orbit around the sun, making it one of the most distant visible objects observed in our solar system.
Its mass is believed to be 20,000 times smaller than Earth’s and about 50 times less than Pluto’s. Though slightly smaller than Ceres—the smallest recognized dwarf planet—its shape has not been resolved due to its extreme distance.
The discovery could challenge current assumptions about the distribution of trans-Neptunian objects (TNOs), which orbit beyond Neptune. These objects often cluster in a way that has led scientists to hypothesize the existence of a hidden giant planet, sometimes called Planet Nine or Planet X.
However, Cheng notes that 2017 OF201 appears to be an outlier to this clustering. “The existence of 2017 OF201 as an outlier to such clustering could potentially challenge this hypothesis,” he said.
Current technology limits detection of objects beyond about 150 AU, meaning hundreds of similarly sized objects could still be undiscovered.
“This single object suggests that the space beyond Neptune is not empty, but rather holds many secrets waiting to be uncovered,” Cheng said.
The five officially recognized dwarf planets in the solar system are Ceres, Pluto, Haumea, Makemake, and Eris. Planets are defined as bodies orbiting the sun that have cleared their orbital neighborhoods, while dwarf planets meet all criteria except they have not cleared their orbits of other objects.
