42355 Typhon ( /ˈtaɪfɒn/; from Greek: Τυφών) is a scattered disc object that was discovered on February 5, 2002, by the NEAT program. It measures 134±13 km in diameter, and is named after Typhon, a monster in Greek mythology.
A large moon was identified in 2006. It is named Echidna—formal designation (42355) Typhon I Echidna, /ɨˈkɪdnə/, from Greek: Έχιδνα—after Echidna, the monstrous mate of Typhon. It orbits Typhon at ~1300 km, completing one orbit in about 11 days. Its diameter is estimated to be 78±8 km. Typhon is considered the first known binary centaur, using an extended definition of a centaur as an object on a non-resonant (unstable) orbit with the perihelion inside the orbit of Neptune.