42355 Typ**hon************** (provisional designation ) is**** a scattered disc**** object**** that**** was discovered**** on**** February**** 5,**** 2002****,**** by**** the NEAT**** program.**** It measures 162 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 89 km.