| Minorplanet: | yes |
| Background: |
|
| 42355 Typhon | |
| Discovered: | 5 February 2002 |
| Mpc Name: | (42355) Typhon |
| Adjectives: | Typhonian |
| Named After: | Τυφών Typhōn |
| Mp Category: | SDO Centaur |
| Epoch: | 13 January 2016 (JD 2457400.5) |
| Semimajor: | 38.263987AU |
| Perihelion: | 17.545721AU |
| Aphelion: | 58.982252abbr=onNaNabbr=on |
| Eccentricity: | 0.5414560 |
| Period: | 236.70 yr (86453.7 d) |
| Inclination: | 2.4252078° |
| Asc Node: | 351.9098598° |
| Arg Peri: | 159.3215723° |
| Mean Diameter: | |
| Rotation: | 9.67abbr=onNaNabbr=on |
| Spectral Type: | B−V= V−R= |
| Abs Magnitude: | 7.5 |
| Albedo: | |
| Mean Motion: | / day |
| Observation Arc: | 9563 days (26.18 yr) |
| Uncertainty: | 2 |
| Tisserand: | 4.692 |
| Satellites: | 1 (Echidna) |
42355 Typhon (; provisional designation ) is a scattered disc object that was discovered on February 5, 2002, by the NEAT program. It measures 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.
| Minorplanet: | yes |
| Echidna | |
| Discovered: | 2006 |
| Mpc Name: | (42355) Typhon I Echidna |
| Adjectives: | Echidnian Echidnean (rarely) (both) |
| Semimajor: | ~1300 km |
| Period: | 11 d |
| Satellite Of: | Typhon |
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 .