(42301) 2001 UR163
, "prov. designation": , is a resonant trans-Neptunian object and possible dwarf planet located in the outermost region of the Solar System. The object measures approximately in diameter with a high albedo and stays in an uncommon orbital resonance (4:9) with Neptune. It has the reddest color (RR-U) of any object in the Solar System. It was discovered on 21 October 2001 by astronomers of the Deep Ecliptic Survey program at Kitt Peak National Observatory near Tucson, Arizona, United States. , it has not been named. Classification and orbit. "" has been characterized as a dwarf planet candidate. Based  on assumptions and estimates, Michael Brown gives it a "likely"-status on his website, which is the third highest status after "near certainty" and "highly likely" "(also see his classification table)". The object orbits the Sun at a distance of 37.0–66.6 AU once every 372 years and 12 months (136,232 days; semi-major axis of 51.82 AU). Its orbit has an eccentricity of 0.29 and an inclination of 1° with respect to the ecliptic. It came to perihelion on 8 October 1937, and has since been moving away from the Sun. In 2006, it moved beyond a distance of 50  AU and is at 53.7 AU . The body's observation arc begins with a precovery, published by the Digitized Sky Survey and taken at the Siding Spring Observatory in July 1982. Numbering and naming. " was numbered (42301) by the Minor Planet Center on 26 May 2002 (). , it has not been named. Acoording to the established naming conventions, it will receive a mythological or mythic name (not necessarily from Classical mythology), in particular one associated with creation. Physical characteristics. Lightcurve analysis shows only small deviations, suggesting that " is a spheroid with small albedo spots. Observations with "Spitzers" Infrared Array Camera were  used to study the body's surface composition. The analyzed data indicate the presence of 20% water ice, 60% amorphous silicates, and 20% organic compounds, including complex ones such as tholins. Diameter and albedo. " measures approximately in diameter with a high albedo of 0.209. Based on previous estimates published on the Lightcurve Data Base and on Michael Brown's website, " measures between and , using an assumed intermediate surface albedo of 0.09 to 0.10 with an absolute magnitude of 4.49 and 4.4, respectively.