moons of Pluto
 |
Pluto and its four known moons. P4
was the latest to be discovered, in 2001 |
Pluto has four known moons. The innermost
of these and by far the largest is Charon,
discovered in 1978. All three of the smaller moons were discovered from
observations by the Hubble Space Telescope: the first two, Hydra (S/2005
P1) and Nix (S/2005 P2), in 2005, and the third, S/2011 P3, in 2011. All
the moons move in retrograde, coplanar, and nearly-circular orbits around
Pluto. Nix, S/2011 P3, and Hydra appear to be in 1:4:5:6 orbital
resonances, respectively, with the Charon-Pluto orbital period.
| moon |
semimajor
axis (km) |
orbital
period (days) |
orbital
eccentricity |
orbital
inclination (o) |
diameter
(km) |
| Charon |
17,536 ± 3 |
6.387 |
0.0022 |
0.001 |
1,207 ± 3 |
| Nix |
48,708 |
24.85 |
0.0030 |
0.195 |
46 – 137 |
| S/2011 P3 |
~59,000 |
32.1 |
~0 |
? |
13 – 34 |
| Hydra |
64,749 |
38.21 |
0.212 |
0.006 |
61 – 167 |
Related category
PLANETS
AND MOONS
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