S/2002 N 4

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S/2002 N 4

Discovery [1]
Discovered by	M.Holman et al. B.Gladman et al.
Discovered	in 2002
Mean Orbital elements [2]
Epoch June 10, 2003
Semi-major axis	48.387 Gm
Eccentricity	0.4945
Inclination	132° *
Orbital period	9374.0 days (25.7 yr)
Physical characteristics
Mean diameter	60 km [2] **
Rotation period	?
Albedo	0.04 assumed [2]
Color	?
Spectral type	?
*to the ecliptic	**based on the albedo

S/2002 N 4 is the outermost irregular natural satellite of Neptune. It was discovered by Matthew J. Holman, Brett J. Gladman, et al. in 2003 from pictures taken in 2002.^{[3] [4]}

S/2002 N 4 orbits Neptune at a distance of more than 48 Gm (million km), making it the most distant known moon of any planet¹. It follows a highly inclined and highly eccentric orbit illustrated on the diagram in relation to other irregular satellites of Neptune. The satellites above the horizontal axis are prograde, the satellites beneath it are retrograde. The yellow segments extend from the pericentre to the apocentre, showing the eccentricity.

S/2002 N 4 is about 60 km in diameter, and assuming the mean density of 1.5 g/cm^{3 [5]} its mass is estimated at 1.6 x 10¹⁷kg.

Given the similarity of the orbit's parameters with Psamathe (S/2003 N1), it was suggested that both irregular satellites could have a common origin in the break-up of a larger moon.^[2].

¹Such distances are of the order of magnitude of heliocentric distances of inner planets rather than moons; at apocenter the satellite is more than 72 Gm (72 million km) from the planet to compare with Mercury's aphelion of ~70 Gm!

[edit] See also

• irregular satellites

[edit] External links

• Matthew Holman's Neptune's page
• David Jewitt's pages
• Scott Sheppard's pages

[edit] References

1. ^ Discovery Circumstances from JPL
2. ^ ^{a b c d} S. Sheppard, D.Jewitt and J.Kleyna A Survey for "Normal" Irregular Satellites Around Neptune: Limits to Completeness, The Astronomical Journal, 132 (2006), pp. 171–176. Preprint.
3. ^ IAU Circular 8213
4. ^ M. Holman, JJ Kavelaars, B. Gladman, Grav, Tommy; Gladman, Brett J; Fraser, Wesley C; Milisavljevic, Dan; Nicholson, Philip D; Burns, Joseph A; Carruba, Valerio; Petit, Jean-Marc; Rousselot, Philippe; Mousis, Oliver; Marsden, Brian G; Jacobson, Robert A Discovery of five irregular moons of Neptune, Nature, 430 (2004), pp. 865-867. Final preprint(pdf)
5. ^ Physical parameters from JPL

• Ephemeris from IAU
• Mean orbital parameters from JPL

v • d • e Moons of Neptune
Naiad · Thalassa · Despina · Galatea · Larissa · Proteus · Triton · Nereid · S/2002 N 1 · S/2002 N 2 · S/2002 N 3 · Psamathe · S/2002 N 4
Neptune Trojans • Rings of Neptune