2017 OF201

2017 OF₂₀₁

Orbit compared to Sedna
Discovery
Discovered by	Sihao Cheng, Jiaxuan Li, Eritas Yang
Discovery site	Cerro Tololo Inter-American Observatory
Designations
MPC designation	2017 OF201
Minor planet category	TNO, SDO and eTNO
Orbital characteristics
Epoch 2025-May-05 (JD 2460800.5)
Uncertainty parameter 3
Observation arc	7.17 yr (2,618 days) (using 19 observations)
Earliest precovery date	2011-08-31
Aphelion	1630 AU (barycentric) 1632±14 AU 1700±60 AU
Perihelion	44.9 AU
Semi-major axis	840 AU (barycentric)
Eccentricity	0.95
Orbital period (sidereal)	24200 years (barycentric) 24300 years (barycentric) 25000±1000 yr
Mean anomaly	1.3°
Mean motion	0° 38m 7.8s / day
Inclination	16.21°
Longitude of ascending node	329°
Time of perihelion	November 1930 ± 1 month
Argument of perihelion	338°
Physical characteristics
Mean diameter	∼ 550 to 850 km (calc. for a typical TNO albedo of 0.15)
Apparent magnitude	22.8
Absolute magnitude (H)	3.5±0.5

2017 OF₂₀₁ is an extreme trans-Neptunian object and dwarf planet candidate, estimated to be at least 550 kilometres (340 miles) in diameter. With an absolute magnitude of between 3 and 4, it may be the brightest known object in the Solar System that does not have a directly estimated size. Its last perihelion was around November 1930. As of 2025, its current distance from the Sun is 90.5 AU, making it one of the most distant Solar System objects observed.

The May 2025 announcement of 2017 OF₂₀₁ may end up disproving the existence of Planet Nine and, possibly, planets beyond Neptune in general. The orientations of the orbits of extreme trans-Neptunian objects tend to cluster. This clustering led to the hypothesis that a possible distant planet has influenced those orbits. However, the orbit of 2017 OF₂₀₁ is one of the few (such as 2013 FT28 and 2015 KG163) that is anti-aligned to the calculated orbit of Planet Nine. Modelling suggests the hypothetical planet would have ejected 2017 OF₂₀₁ from its current orbit over times scales of less than 100 million years, though it could be in a temporary orbit.

Orbit

2017 OF₂₀₁ orbits far beyond Neptune at an average distance of 880 astronomical units (AU), taking around 25,000 years to complete an orbit around the Sun. 2017 OF₂₀₁ has an orbit with an orbital eccentricity of 0.95 and an orbital inclination of 16.2°. 2017 OF₂₀₁ has one of the most distant aphelia of known trans-Neptunian objects, being similar to 2013 SY99 and surpassed by 2019 EU5, all three of which have perihelia inside the Kuiper cliff and so have or have had some interaction with Neptune. This places this object near the estimated boundary of the scattered disc region and the inner Oort cloud when the object is at its maximum distance of about 1,630 astronomical units (0.0258 light-years) from the Sun. The orbit of 2017 OF₂₀₁ is shaped by both Neptune and the galactic tide over billions of years.

Physical characteristics

The diameter of 2017 OF₂₀₁ is unknown, but it is estimated to be somewhere between 550-850 kilometres in diameter, placing it within the range of possible dwarf planets. For reference, Pluto is 2,376.6 kilometres in diameter, and Quaoar, which is widely accepted as a dwarf planet, is 1,090 kilometres in diameter.

External links

• 2017 OF201 at the JPL Small-Body Database
• Spin view of orbit, Sky trajectory 2011-2027 Tony Dunn