 Halimede imaged by theVery Large Telescope during follow-up observations on 3 September 2002 | |
| Discovery[1][2] | |
|---|---|
| Discovered by | |
| Discovery date | August 14, 2002 |
| Designations | |
Designation | Neptune IX |
| Pronunciation | /hæləˈmiːdiː/[3] |
Named after | ἉλιμήδηHalimēdē |
| S/2002 N 1 | |
| Adjectives | Halimedean/ˌhæləməˈdiːən/ |
| Orbital characteristics[4] | |
| Epoch June 10, 2003 | |
| 16,611,000 km | |
| Eccentricity | 0.2646 |
| 1,879.08 d (5.1446 a) (retrograde) | |
| Inclination | 134.1° |
| Physical characteristics | |
| 62 km(for albedo 0.04)[5] | |
| Albedo | 0.04(assumed)[5] |
Spectral type | neutral (grey) B-V=0.73 R-V=0.35[6] |
Halimede/hæləˈmiːdiː/, orNeptune IX, is aretrogradeirregular satellite ofNeptune. It was discovered byMatthew J. Holman,John J. Kavelaars,Tommy Grav, Wesley C. Fraser andDan Milisavljevic on August 14, 2002.[7]
Halimede, like many of the outer satellites ofNeptune, is named after one of the Nereids, the fifty daughters ofNereus andDoris. Before the announcement of its name on February 3, 2007 (IAUC 8802), Halimede was known by the provisional designation S/2002 N 1.
Halimede has the second mosteccentric and third mostinclined orbit around Neptune.[8] This is illustrated on the diagram in relation to other irregular satellites of Neptune. The satellites above the horizontal axis areprograde, the satellites beneath it areretrograde. The yellow segments extend from thepericentre to theapocentre, showing the eccentricity. It is also worth mentioning thatSao andLaomedeia are similar to Halimede but they both have prograde orbits unlike Halimede which has a retrograde orbit.[9]
Halimede is about 62 kilometers in diameter (assuming analbedo of 0.04)[5] and appears neutral (grey) in thevisible light. Given the very similar colour of the satellite to that ofNereid together with the high probability (41%[7]) of collision in the past lifespan of the Solar System, it has been suggested that the satellite could be a fragment of Nereid.[6]
Listed in approximately increasing distance fromNeptune | |||||||||||
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