(84522) 2002 TC302

' (provisional designation ') is a mid-sized trans-Neptunian object located in the outermost region of the Solar System. It was discovered on 9 October 2002, by American astronomers Mike Brown, Chad Trujillo and David Rabinowitz at the Palomar Observatory in California. The resonant trans-Neptunian object stays in a 2:5 resonance with Neptune. It has a reddish color, a rotation period of 56.1 hours and measures at least 500 km in diameter.

Orbit and classification
orbits the Sun at a distance of 39.2–71.4 AU once every 410 years and 12 months (150,105 days; semi-major axis of 55.28 AU). Its orbit has an eccentricity of 0.29 and an inclination of 35° with respect to the ecliptic. In December 2058, It will come to perihelion (minimum distance from the Sun) at 39.2 AU, which is about the same as Pluto's semi-major axis (average distance from the Sun). Given the long orbit that TNOs have around the Sun, comes to opposition in late October of each year at an apparent magnitude of 20.5.

Both the Minor Planet Center (MPC) and the Deep Ecliptic Survey (DES) show to be a resonant trans-Neptunian object in a 2:5 resonance with Neptune, meaning it completes two orbits for every five orbits of Neptune.

Physical characteristics


has an absolute magnitude of 3.78. It has an estimated diameter of $543$. Using the Spitzer Space Telescope, it was previously estimated to have a diameter of $460 km$, which would have made it one of the largest TNOs. This overestimation was due to insufficient motion to allow for a good sky subtraction, and because was very close to a brighter background object. Brown noted that the Spitzer measurement involved a very large potential error and that the object would likely be much smaller.

The red spectra suggests that has very little fresh ice on its surface. Its rotation period was initially estimated by Thirouin et al. to be 5.41 h, based on a light-curve amplitude of $500 km$. However, this short rotation period was most likely an alias due to a bias for shorter and more easily discernable shorter periods. is highly oblate, and Ortiz et al. suggest a longer rotation period estimate of 56.1 hours.

An occultation of a 15.3 magnitude star by on 28 January 2018 over Europe suggests that it has highly oblate shape with dimensions of $584.1 km$ × $56.1 h$ and a projected axial ratio of a/c=1.18. The area equivalent diameter of is $0.147$.

On 11 November 2021, an occultation across North America and Europe detected an oblate shape of $0.115$ km (mean 499 km), in strong agreement with the 2018 occultation results. No satellites were detected.

Possible satellite
The mean diameter of determined from occultations in 2018 is smaller than the larger diameter estimate of $1.03$ by Spitzer in 2008. Despite the large uncertainty in the Spitzer's estimate, the difference of $0.67$ between the two diameters is significant, implying that may have a large satellite with a possible size range of $4.17$, nearly as large as  itself. This possible satellite is expected to orbit at a very close distance of less than $584.1 km$, close enough to slow down 's rotation through tidal interactions.

If both the primary body and satellite are doubly tidally locked, then the expected orbital period of the satellite would be approximately 54 hours, equal to 's rotation. Given an orbital period of 54 hours, the satellite's estimated orbital separation from the primary would be $1,145 km$, with an angular separation of 58 milliarcseconds, too small to be resolved with current space telescopes such as Hubble. Under the assumption the satellite's diameter is $0.04 mag$, it would cause 's position to oscillate by 18 milliarcseconds as it orbits around its barycenter.