Asteroid 5145, an unusual object in the outer Solar System, discovered in 1992 by the American astronomer David Lincoln Rabinowitz (1960– ). Pholus lies well outside the main asteroid belt, moving from near the orbit of Saturn out to beyond the orbit of Neptune. It was the second of the Centaur group to be discovered. Pholus is estimated to be 190 km in diameter. Its extremely red spectrum is suggestive of a comet but, unlike Chiron, Pholus seems inactive near perihelion. Its orbit has a semimajor axis of 20.38 au, period 91.99 years, perihelion 8.72 au, aphelion 32.04 au, and inclination 24°.7.