Tyche (minor planet designation: 258 Tyche) is a relatively large main belt asteroid discovered by Robert Luther at Düsseldorf-Bilk Observatory on 4 May 1886. The stony S-type asteroid measures about 65 kilometers in diameter and has a perihelion of 2.1 AU. Tyche orbits very close to the Eunomia family of asteroids, and could be a member based on composition. However, it is larger than all family members apart from 15 Eunomia while lying at the very edge of the family group. Hence, there is a good chance that it is an unrelated interloper. There is some uncertainty regarding Tyche's rotation period. Various authors give values from 9.983 to 10.041 hours. It was named after Greek goddess of fortune, Tyche, which is also the name of one of the Oceanids. Tyche's Roman equivalent is Fortuna, after which the asteroid 19 Fortuna is named. References External links The Asteroid Orbital Elements Database Minor Planet Discovery Circumstances Asteroid Lightcurve Data File Ephemeris Eunomia asteroids Background asteroids Tyche Tyche S-type asteroids (Tholen) S-type asteroids (SMASS) 18860504