258 Tyche is a relatively large main beltasteroid discovered in 1886. It is classified as an S-type. 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.