NSDC/Natural Satellites Data Center 
 GUIDE FOR THE SATELLITES OF NEPTUNE 
The planet Neptune has rings and three families of satellites, orbiting around it: The tables below provide the main characteristics of these satellites. In order to get more information on these satellites, click on their names.

The rings

Rings and inner satellites  Distance to the 
centre of Neptune		 Size of the ring Albedo
1989 N3R (Galle) 41 900 km 15 km very small
satellite Naïad (N-3) 48 227 km - -
satellite Thalassa (N-4) 50 075 km - -
satellite Despina (N-6) 52 526 km - -
1989 N2R (Le Verrier) 53 200 km 15 km very small
1989 N4R (Lassell, Arago) 53 200 km 5 800 km very small
satellite Galatea (N-6) 61 953 km - -
1989 N1R (Adams) 62 930 km less than 50 km very small
 The thickness of the rings of Neptune is unknown.
 
The faint inner satellites
satellites:
a in km
P in days
eccentricity
inclination
on neptunian equator
d in km
mv
ap in
arcsec
Naiad - N 3
48 227
0.294 40
0.000 33
4.74°
58
24.7
2.3
Thalassa - N 4
50 075
0.311 48
0.000 16
0.21°
80
23.8
2.4
Despina - N 5
52 526
0.334 66
0.000 139
0.07°
148
22.6
2.5
Galatea - N 6
61 953
0.428 75
0.000 12
0.05°
158
22.3
3.0
Larissa - N 7
73 548
0.554 65
0.001 39
0.20°
208 x ? x 178
22.0
3.5
Proteus - N 8
117 647
1.122 32
0.000 44
0.04°
436 x 416 x 402
20.3
5.6
a=semi-major axis; P= period of revolution; d=diameter; mv= visual magnitude at opposition; ap= apparent distance to Neptune at opposition
the size d is provided as: equatorial sub-planet diameter, equatorial diameter along the orbit and polar diameter of the triaxial ellipsoid
 
The main inner satellite
 
Triton - N 1
semi-major axis in km
354 759
period of revolution
5.876 85 d
eccentricity
0.000 02
inclination on the neptunian equator
156.3 °
size in km
2705.2
highest magnitude at the opposition
13.7
maximum apparent geocentric distance
to Neptune at opposition
17 arcsec
 the size is provided as: equatorial sub-planet diameter, equatorial diameter along the orbit and polar diameter of the triaxial ellipsoid
 
The main outer satellite
 
Nereid - N 2
semi-major axis in km
5 513 410
period of revolution
360.135 d
eccentricity
0.751
inclination on the neptunian equator
6.68 °
size in km
340
highest magnitude at the opposition
18.7
maximum apparent geocentric distance
to Neptune at opposition
4 min 24 arcsec
 the size is provided as: equatorial sub-planet diameter, equatorial diameter along the orbit and polar diameter of the triaxial ellipsoid
 

The faint outer satellites

satellites:

a in km

a in AU

P in years

eccentricity

inclination on the ecliptic

d in km

mv

ap in min of degree

Halimede - N 9 (S/2002 N1)

15 728 000

0.1051

5.15

0.571

134°.1

61

24.5

19 min

Sao - N 11 (S/2002 N2)

22 422 000

0.1499

7.98

0.293

48.5°

40

25.4

27 min

Laomedeia - N 12 (S/2002 N3)

23 571 000

0.1576

8.67

0.424

138°

40

25.4

28 min

Psamathe - N 10 (S/2003 N1)

46 695 000

0.3121

24.96

0.450

137°.4

38

25.6

56 min

Neso - N 13 (S/2002 N4) 48 387 000 0.3234 26.66 0.495 132°.6 60 24.6 58 min
a=semi-major axis; P= period of revolution; d=diameter; mv= visual magnitude at opposition; ap= apparent semi major axis at opposition
the size d is provided as: equatorial sub-planet diameter, equatorial diameter along the orbit and polar diameter of the triaxial ellipsoid
 

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