Dwarf Planet
Orcus
Locked in the same 2:3 resonance with Neptune as Pluto, but always on the opposite side of its orbit — hence the nickname "anti-Pluto". Crystalline water ice and traces of ammonia hint at past cryovolcanism.
| Type | Dwarf Planet |
|---|---|
| Parent body | Sun |
| Radius | 455 km · 0.0714 R⊕ |
| Mass | 6.350 × 10²⁰ kg · 1.06 × 10⁻⁴ M⊕ |
| Mean density | 1.61 g/cm³ |
| Surface gravity | 0.205 m/s² · 0.021 × Earth |
| Escape velocity | 0.432 km/s |
| Rotation period | 13.2 hours |
| Orbital radius | 39.4 AU (Sun) |
| Eccentricity | 0.226 |
| Orbital period | 248 years |
| Discovery | 2004, Brown, Trujillo, Rabinowitz |
| Moon | Vanth |
| Resonance | 2:3 (Neptune) |