42355 Typhon

42355 Typhon (provisional designation ) is a scattered disc object that was discovered on February 5, 2002, by the NEAT program. It measures $138 km$ in diameter, and is named after Typhon, a monster in Greek mythology.

Typhon is 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.

Moon
A large moon was identified in 2006. It is named Echidna (formal designation (42355) Typhon I Echidna), after the monstrous mate of Typhon. It orbits Typhon at ~1300 km, completing one orbit in about 11 days. Its diameter is estimated to be $162 km$.