Astronomers Identify Potential Dwarf Planets Orbiting Every 25,000 Years

The recently identified Transneptunian object, which was named in 2017, stands out as one of the most prominent objects in our solar system, measuring approximately 700 km in diameter, thus qualifying as a dwarf planet.

Transneptunian Objects (TNOs) are small celestial bodies that orbit the Sun at distances greater than that of Neptune.

In the 30 years following the discovery of the first TNO outside Pluto, numerous research initiatives have been launched to explore the expansive regions of the outer solar system, resulting in the identification of over 5,000 TNOs to date.

The newly discovered TNO is significant for two main reasons: its unique trajectory and substantial size.

“The object’s aphelion—the furthest point in its orbit from the Sun—is over 1,600 times the distance of Earth’s orbit,” states Dr. Sihao Chen, an astronomer at the Institute of Advanced Research and Boundary Research.

“Conversely, its perihelion—the closest point in its orbit to the Sun—is 44.5 times that of Earth’s orbit, akin to Pluto’s orbit.”

“This extreme trajectory takes around 25,000 years to complete, suggesting a complex gravitational history,” he adds.

“We likely experienced a close encounter with a massive planet, compelling us into this wide orbit,” comments Princeton University astronomer Dr. Elitas Yang.

“There may have been multiple phases in this transition.”

“The object might have initially been ejected into the Oort Cloud, the outermost region of the solar system, which is home to numerous comets.”

“Many extreme TNOs appear to follow similar trajectories, but 2017 OF201 stands out as an anomaly,” remarks Dr. Jiaxuan Li, also from Princeton University.

“This clustering is interpreted as indirect evidence suggesting the presence of another celestial body, often referred to as Planet X or Planet Nine, which could be influencing these objects through gravitational forces.”

“The existence of 2017 OF201 as an outlier in this clustering could potentially challenge this hypothesis.”

Astronomers estimate the diameter of 2017 OF201 to be 700 km, making it the second-largest object on such an extensive orbit.

“2017 OF201 can only be detected about 1% of the time when it is relatively close to us,” Dr. Chen notes.

“The presence of this solitary object implies that there may be around 100 other similar objects with comparable trajectories and sizes.”

Researchers discovered 2017 OF201 as part of an ongoing initiative to identify TNOs and potential new planets in the outer solar system.

The detection involved identifying bright spots in astronomical image databases from the Victor M. Blanco Telescope and the Canada France Hawaii Telescope (CFHT), as well as attempting to trace groups of possible spots that indicate TNO movement across the sky.

Scientists identified 2017 OF201 in 19 different exposures collected over a span of seven years.

“Although advancements in telescopic technology have allowed us to explore distant realms of the universe, much remains to be uncovered within our own solar system,” concludes Dr. Chen.

The team’s paper has been published online at arxiv.org.

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Sihao Cheng et al. 2025. Discovery of new planet candidates in extremely wide orbits: 2017 OF201. arxiv: 2505.15806