Resonant trans-Neptunian object | Wikipedia audio article
(42301) 2001 UR163, provisional designation 2001 UR163, is a resonant trans-Neptunian object and possible dwarf planet located in the outermost region of 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. The object measures approximately 600 kilometers in diameter and stays in an orbital resonance with Neptune (4:9). It has the reddest color of any object in the Solar System.