Hippocamp (moon)
Hippocamp, also designated Neptune XIV, is a small moon of Neptune discovered on 1 July 2013. It was found by astronomer Mark Showalter by analyzing archived Neptune photographs the Hubble Space Telescope captured between 2004 and 2009. The moon is so dim that it was not observed when the Voyager 2 space probe flew by Neptune and its moons in 1989. It is about 35 km (20 mi) in diameter, and orbits Neptune in about 23 hours, just under one Earth day. Due to its unusually close distance to Neptune's largest inner moon Proteus, it has been hypothesized that Hippocamp may have accreted from material ejected by an impact on Proteus several billion years ago. The moon was formerly known by its provisional designation S/2004 N 1 until February 2019, when it was formally named Hippocamp, after the mythological sea-horse symbolizing Poseidon in Greek mythology.
Composite of Hubble images from 2009 showing Neptune, its rings, and inner moons including Hippocamp (circled) | |
| Discovery | |
|---|---|
| Discovered by | M. R. Showalter I. de Pater J. J. Lissauer R. S. French |
| Discovery date | 1 July 2013 |
| Designations | |
Designation | Neptune XIV |
| Pronunciation | /ˈhɪpəkæmp/ |
Named after | ἱππόκαμπος hippokampos |
Alternative names | S/2004 N 1 |
| Adjectives | Hippocampian /hɪpəˈkæmpiən/ |
| Orbital characteristics | |
| Epoch 1 January 2020 (JD 2458849.5) | |
| Earliest precovery date | 6 November 2004 |
Semi-major axis | 105,283 km |
| Eccentricity | 0.00084±0.00032 |
Orbital period (sidereal) | 0.95 d (22.8 h) |
Mean anomaly | 329.901° |
| Inclination | 0.0641°±0.0507° (to Neptune's equator) 0.0019° (to local Laplace plane) |
Longitude of ascending node | 110.467° |
| 305.446° | |
| Satellite of | Neptune |
| Physical characteristics | |
Mean radius | 17.4±2.0 km |
| Mass | (1.029–30.87)×1015 kg |
Synodic rotation period | synchronous |
| Albedo | ≈0.09 (assumed) |
| 26.5±0.3 | |