| Name |
Diameter(s)
(km) |
Mean Distance
From Planet
(×103 km) |
Rotational
Period
(days) |
Orbital
Period
(days) |
Orbital
Inclination |
Orbital
Eccentricity |
Albedo
(%) |
|---|
|
The Inner Regular Satellites
|
| Naiad |
58 |
48.227 |
|
0.294396 |
4.74° |
0.000 |
6 |
| Thalassa |
80 |
50.075 |
|
0.311485 |
0.205° |
0.000 |
6 |
| Despina |
148 |
52.526 |
|
0.334655 |
0.065° |
0.000 |
6 |
| Galatea |
158 |
61.953 |
|
0.428745 |
0.054° |
0.000 |
6 |
| Larissa |
208 × 178 |
73.548 |
|
0.554654 |
0.201° |
0.00139 |
6 |
| Proteus |
436 × 416 × 402 |
117.647 |
|
1.122315 |
0.039° |
0.0004 |
6 |
|
Peculiar Triton
|
| Triton |
2,705.2 |
354.76 |
5.876854 |
-5.876854 |
157.345° |
0.000016 |
77 |
|
Irregular Outer Satellites
|
| Nereid |
340 |
5,513.4 |
|
360.13619 |
7.23° |
0.7512 |
40 |
| S/2002 N1 |
61 |
15,686 |
|
-1,874.8 |
134.1° |
0.572 |
|
| S/2002 N2 |
40 |
22,337 |
|
2,925.6 |
52.74° |
0.137 |
|
| S/2002 N3 |
40 |
22,613 |
|
2,980.4 |
39.56° |
0.416 |
|
| S/2003 N1 |
38 |
46,738 |
|
-9,136.1 |
137.3° |
0.450 |
|
| S/2002 N4 |
60 |
47,279 |
|
-9,007.1 |
139.3° |
0.605 |
|
Name
The satellites of Neptune have Greek and Roman names associated with Neptune, the god of the sea. Un-named satellites are in blue.
Diameter
Triton is by far Neptune's largest satellite. The rest are small bodies.
Mean Distance From Planet
The satellites are all spread out up to 47 million km, much further than any other planet's satellites.
Rotational and Orbital Periods
Triton rotates in the same period as it revolves around the planet. This is caused by the strong tidal forces exerted by the planet on the satellite. A planet's outer satellites are less affected by tidal forces.
As seen from above the north pole of the Earth, most of the planets and satellites revolve in an anticlockwise direction. This is called Direct or Prograde Motion. Some satellites revolve in a clockwise sense. This is called Retrograde Motion. Triton revolves in the retrograde direction, the only large satellite in the Solar System to do so.
Of Neptune's seven outer satellites, three are retrograde.
Orbital Inclination
This is the angle of inclination of the satellite orbits compared to the planet's equatorial plane. Most of Neptune's satellites orbit very close to the planet's equator. Triton has the most inclined orbit for a large satellite in the Solar System.
The planet's outer satellites also have highly inclinded orbits.
Orbital Eccentricity
The orbits of Neptune's inner satellites are nearly circular. The outer satellites have elliptical orbits. Until 2004, Nereid had the most eccentric orbit of a satellite in the Solar System.
Albedo
This is the percentage of sunlight that is reflected by the satellites. Most of Neptune's satellites are dark bodies. Triton, with its surface covered with frozen Nitrogen, is very reflective.
