Neptunian Satellite Fact Sheet

[Image of Neptune]

Bulk parameters

                              Mass          Radius       Mean density    Visual geometric albedo
                           (1020 kg)         (km)          (kg/m3)
  Naiad (NIII)                0.002      48 x 30 x 26                            0.07
  Thalassa (NIV)              0.004      54 x 50 x 26                            0.09
  Despina (NV)                0.02       90 x 74 x 64                            0.09
  Galatea (NVI)               0.04      102 x 92 x 72                            0.08
  Larissa (NVII)              0.05     108 x 102 x 84                            0.09
  Proteus (NVIII)             0.5      220 x 208 x 202                           0.10
  Triton (NI)               214.           1,353.4          2,050                0.76
  Nereid (NII)                0.3            170                                 0.16

  Halimede (NIX, S/2002 N1)   0.001           30                                 0.16
  Sao (NXI, S/2002 N2)        0.001           20                                 0.16
  Laomedeia (NXII, S/2002 N3) 0.001           20                                 0.16
  Neso (NXIII, S/2002 N4)                     30                                                      
  Psamathe (NX, S/2003 N1     0.0002          20                                 0.16

Orbital parameters

                                                                Orbital   Rotation 
                                      Semimajor axis            Period*    Period   Inclination  Eccentricity
                                 (103 km)  (Neptunian Radii)    (days)     (days)    (degrees)
  Naiad (NIII)                    48.227        1.948          0.294396                4.74        0.0003
  Thalassa (NIV)                  50.075        2.022          0.311485                0.21        0.0002
  Despina (NV)                    52.526        2.121          0.334655                0.07        0.0001
  Galatea (NVI)                   61.953        2.502          0.428745                0.05        0.0001
  Larissa (NVII)                  73.548        2.970          0.554654                0.20        0.0014
  Proteus (NVIII)                117.647        4.751          1.122315                0.04        0.0004
  Triton (NI)                    354.76        14.328          5.876854R     S       157.345       0.000016
  Nereid (NII)                 5,513.4        222.67         360.13619                 7.23        0.7512

  Halimede (NIX, S/2002 N1)    15730.         635.2         1879.7R                  134.1         0.571     
  Sao (NXI, S/2002 N2)         22420.         905.3         2914.1                    48.5         0.293  
  Laomedeia (NXII, S/2002 N3)  23570.         951.8         3167.9                    34.7         0.424                    
  Psamathe (NX, S/2003 N1      46700.        1885.8         9115.9R                  137.4         0.450
  Neso (NXIII, S/2002 N4)      48390.        1954.0         9374.0R                  132.6         0.495
*R indicates retrograde motion
S indicates synchronous rotation - the rotation period is the same as the orbital period
Neptune's Known Satellites - Carnegie Institution, DTM

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Author/Curator:
Dr. David R. Williams, dave.williams@nasa.gov
NSSDC, Mail Code 690.1
NASA Goddard Space Flight Center
Greenbelt, MD 20771
+1-301-286-1258

NASA Official: Ed Grayzeck, edwin.j.grayzeck@nasa.gov
V1.0, 14 July 1995
Last Updated: 22 January 2008, DRW