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Encyclopedia > Pluto > Satellites I
SATELLITES OF PLUTO
Discovered in 1978 by Harrington and Christy, Charon (Pluton I) form with Pluto a double planet because of their respective sizes and the small distance between them.
In 2005, it was discovered two new satellites beyond Charon: Nix (or Nyx) and Hydra; in 2011, another satellite orbiting S/2011P1 between Nyx and Hydra and in 2012 a satellite S/2012P1 beyond Hydra.
| |
Charon | Styx | Nix | Kerberos | Hydra |
|---|---|---|---|---|---|
| semi-major axis of the orbit in km |
17 536 | 42 000 | 48 708 | 59 000 | 64 749 |
| average diameter in km |
1207 | 10 to 25 | 46 to 137 | 13 to 34 | 61 to 167 |
| visual magnitude | 16.8 | 27 | 23.7 | 26 | 23.3 |
| revolution period in days |
6.387 | 20.2 | 24.856 | 32.1 | 38.206 |
| rotation period in days |
6.387 | - | - | - | - |
| orbital velocity | 0.22 km/s | 0.15 km/s | 0.14 km/s | 0.13 km/s | 0.12 km/s |
| inclination of the orbit on the equator of Pluto (retrograde) |
177° | 177° | 177° | 177° | 177° |
| eccentricity of the orbit | 0.0022 | 0.0 | 0.0030 | 0 | 0.0051 |
| mass (Pluto=1) | 0.1567 | - | - | - | - |
| density (water=1) | 2 | - | - | - | - |
| escape velocity | 610 m/s | - | - | - | - |
| reflectivity (geometric albedo ) | 0.5 | - | - | - | - |