Hiʻiaka (moon)
In this photo taken by the Hubble Space Telescope, Hiʻiaka is the brighter spot near the top, directly on top Haumea (center). | |
| Discovery | |
|---|---|
| Discovered by | |
| Discovery site | W. M. Keck Obs., Mauna Kea |
| Discovery date | 26 January 2005 |
| Designations | |
Designation | (136108) Haumea I |
| Pronunciation | /hiːʔiˈɑːkə/ Hawaiian: [ˈhiʔiˈjɐkə] |
Named after | Hiʻiaka |
| S/2005 (2003 EL61) 1 S/2005 (136108) 1 | |
| Orbital characteristics | |
| Epoch 28 May 2008 12:00 UT (JD 2454615.0) | |
| 49371±45 km | |
| Eccentricity | 0.0542±0.0012 |
| 49.462±0.083 d | |
| 154.53°+2.05° −2.00° | |
| Inclination |
|
| 13.110°+0.030° −0.031° (to ecliptic) | |
| 98.34°+2.02° −2.06° | |
| Satellite of | Haumea |
| Physical characteristics | |
| Dimensions |
|
| 370±20 km (volume equivalent) | |
| Mass | (1.6±0.2)×1019 kg (2025) (1.2±0.3)×1019 kg (2024) |
Mean density | 0.640±0.080 g/cm3 |
| 9.68±0.02 h | |
| ≈ 0° wrt Haumea | |
| Albedo | 0.74±0.15 |
| Temperature | ≈ 40 K (same as Haumea) |
| ~ 20 | |
| 3.21±0.12 (average) | |
Hiʻiaka, formal designation (136108) Haumea I, is the larger, outer moon of the trans-Neptunian dwarf planet Haumea. Discovered by Michael E. Brown and the Keck Observatory adaptive optics team on 26 January 2005, it is named after Hiʻiaka, the patron goddess of the Big Island of Hawaii and one of the daughters of Haumea. The moon follows a slightly elliptical orbit around Haumea every 49.5 days, at a distance of 49,400 km (30,700 mi).
Hiʻiaka is an elongated and irregularly shaped body with a mean diameter of 370 km (230 mi), making it the sixth-largest known moon of a trans-Neptunian object. It has a very low bulk density of 0.64 g/cm3, which indicates it is mostly made of loosely-packed water ice and rock. Telescope observations have shown that Hiʻiaka has a highly reflective surface made of crystalline water ice, much like Haumea itself. Hiʻiaka rotates about its axis every 9.68 hours. Like its smaller sibling moon Namaka, Hiʻiaka is believed to be a fragment of Haumea that was ejected in the aftermath of a giant impact 4.4 billion years ago.