(55637) 2002 UX25 - 18th Largest TNO? 7th Largest Cubewano ?

2002 UX25 is a large trans-Neptunian object. 2002 UX25 is possibly the 18th largest TNO and 7th largest Cubewano currently known.

Discovery

2002 UX25 was discovered on October 30, 2002, by the Spacewatch program at Kitt Peak.

2002 UX25 has precovery images back to 1991.

Stats

Estimated Diameter: 681 km (567 - 797 km)
Aphelion: 48.92 AU
Perihelion: 36.77 AU
Semi-major axis: 42.94 AU
Orbital Period: 281.41 years
Rotation period: 14.38 hours
Date discovered: 2002.10.30
Satellite: 1
Classification: TNO, KBO - Cubewano

Orbit

2002 UX25 is a Spitzer dwarf-planet candidate that orbits the Sun in the Kuiper belt beyond Neptune. It takes roughly 281 years to orbit the Sun.

2002 UX25 has a perihelion (closest approach to the Sun) of 36.77 AU, which it will next reach in 2065. As of 2010, 2002 UX25 is 41 AU from the Sun.

Physical Characteristics

A variability of the visual brightness was detected which could be fit to a period of 14.38 or 16.78 h rotation period (depending on a single-peaked or double peaked curve).

The Spitzer Space Telescope has estimated it to have a size of 681 +116 or
−114 km.

Satellite

The discovery of a satellite of 2002 UX25 was reported in IAUC 8812 on 22 February 2007.

The satellite was detected using the Hubble Space Telescope in August 2005. The orbit of this satellite has yet to be determined. The satellite was found at 0.16 arcsec from the primary with an apparent magnitude difference of 2.5. Assuming a similar albedo the magnitude suggests the satellite has a diameter of 205 ± 55 km.

How big is it?

2002 UX25 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.

Dwarf planet candidate?

2002 UX25 has an absolute magnitude of 3.6, making it a dwarf planet candidate. The Spitzer Space Telescope has estimated 2002 UX25 to have a diameter of about 681 km, and most icy objects around 400 km in diameter are believed to be spherical.

Michael E. Brown's automatically updated website lists it as a highly likely dwarf planet, and Michael E. Brown called it a probable dwarf planet. But light curve analysis has questioned whether it would truly qualify as a dwarf planet.