(84522) 2002 TC302 - 8th Largest TNO?

2002 TC302 is a large, red 2:5 resonant trans-Neptunian object.

Discovery

2002 TC302 is discovered on October 9, 2002, by Michael E. Brown's team at the Palomar Observatory.

Stats

Estimated Diameter: 1150 km
Aphelion: 71.87 AU
Perihelion: 39.20 AU
Semi-major axis: 55.54 AU
Orbital Period: 413.86 years
Rotation period: ? hrs
Date discovered: 2002.10.9
Satellite: ?
Classification: TNO, 2:5 resonance

Orbit

Both the Minor Planet Center (MPC) and the Deep Ecliptic Survey (DES) show this dwarf-planet candidate to be in a 2:5 resonance with Neptune. Due to the resonance, it completes 2 orbits for every 5 orbits of Neptune.

As of 2009, it is the largest dwarf-planet candidate that is known to be in a (non-plutino) resonance with Neptune.

Surface and albedo

The red spectra suggests that 2002 TC302 has very little fresh ice on its surface and may explain why it has a lower-than-average estimated albedo of ~0.03.

Large dwarf-planet candidate

2002 TC302 has an absolute magnitude (H) of 3.87, and the Spitzer Space Telescope has estimated it to have a diameter of 1145.7 ± 325 km. This qualifies it as one of the largest dwarf-planet candidates.

However, Brown notes that the measurement involves a very large potential error, and that the object is likely smaller, making its chances of being a dwarf planet "highly likely" rather than "virtually certain", as it would be if it were actually 1100 km in diameter.

How big is it?

2002 TC302 is so far away in the outer solar system that we don't know for sure how large it is. Because all we see is a dot of light, which is sunlight reflected off the surface of the TNO. But we don't know if the object is bright because it is large or if it is bright because it is highly reflective or both.