Vanth (moon)
Vanth (smaller object) and Orcus imaged by the Hubble Space Telescope | |
| Discovery | |
|---|---|
| Discovered by |
|
| Discovery date | 13 November 2005 |
| Designations | |
Designation | (90482) Orcus I |
| Pronunciation | /ˈvænθ/ |
Named after | Vanth |
| Adjectives | Vanthian |
| Orbital characteristics | |
| Epoch 21.5 September 2006 (JD 2454000.0) | |
| 8999.8±9.1 km | |
| Eccentricity | 0.00091±0.00053 |
| 9.539154±0.000020 d | |
| Inclination | 105.03°±0.18° (to celestial equator) 90.54°±0.17° (to ecliptic) |
| 53.49°±0.33° | |
| 274.51° | |
| Satellite of | Orcus |
| Physical characteristics | |
| 442.5±10.2 km (occultation) 475±75 km (thermal) | |
| Mass | (8.7±0.8)×1019 kg |
Mean density | ≈1.9±0.3 g/cm3 (occultation) 1.5+1.0 −0.5 g/cm3 (thermal) |
| synchronous | |
| Albedo | 0.08±0.02 |
| Temperature | <44 K |
Spectral type | moderately red V–I = 1.03±0.05 |
| 21.8 | |
| 4.88±0.05 | |
Vanth (formal designation (90482) Orcus I) is the only known moon of the large trans-Neptunian dwarf planet Orcus. It was discovered by Michael Brown and Terry-Ann Suer using images taken by the Hubble Space Telescope on 13 November 2005. The moon has a diameter of 443 km (275 mi), making it about half the size of Orcus and the third-largest moon of a trans-Neptunian object. Vanth is massive enough that it shifts the barycenter of the Orcus–Vanth system outside of Orcus, forming a binary system in which the two bodies revolve around the barycenter, much like the Pluto–Charon system. It is hypothesized that both systems formed similarly, most likely by a giant impact early in the Solar System's history. Compared to Orcus, Vanth has a darker and slightly redder surface that supposedly lacks exposed water ice, resembling primordial Kuiper belt objects.