Hiʻiaka is above Haumea (center) in this Keck telescope image.
|Discovered by||Michael E. Brown,
David Rabinowitz, et al.
|Discovery date||26 January 2005|
|MPC designation||Haumea I Hiʻiaka|
|(136108) 2003 EL61 I,
S/2005 (2003 EL61) 1
|Mass||(1.79±0.11)×1019 kg(0.45% of Haumea)|
|3.3 difference from primary's 17.3|
Discovery and naming
Hiʻiaka was the first satellite discovered around Haumea. It is named after one of the daughters of Haumea, Hiʻiaka, the patron goddess of the Big Island of Hawaii, though at first it had gone by the nickname "Rudolph" by its discovery team. It orbits once every 49.12±0.03 d at a distance of 49880±198 km, with an eccentricity of 0.0513±0.0078 and an inclination of 126.356±0.064°. Mutual events expected in July 2009 should improve the knowledge of the orbits and masses of the components of the Haumean system.
Size and brightness
Its measured brightness is 5.9±0.5%, translating into a diameter of about 22% of its primary, or in the range of 350 km, assuming similar albedo. To put this in perspective, this would make it larger than all but four of the asteroids, after 1 Ceres, 2 Pallas, 4 Vesta, and 10 Hygiea. Future exploration of Haumea and its moons could reveal that Hiʻiaka is in hydrostatic equilibrium, i.e. rounded by its own gravity. However, it is not a dwarf-planet candidate because it is a moon.
Spectrum and composition
The near infrared spectrum of Hiʻiaka is dominated by water-ice absorption bands, which means that its surface is made mainly of water ice. The presence of the band centered at 1.65 µm indicates that the surface water ice is primarily in the crystalline form. Currently it is unclear why water ice on the surface has not turned into amorphous form as would be expected due to its constant irradiation by cosmic rays.
- The Hawaiian pronunciation is [ˈhiʔiˈjɐkə].
- Ragozzine, D.; Brown, M. E. (2009). "Orbits and Masses of the Satellites of the Dwarf Planet Haumea (2003 EL61)". The Astronomical Journal 137 (6): 4766. arXiv:0903.4213. Bibcode:2009AJ....137.4766R. doi:10.1088/0004-6256/137/6/4766.
- Dumas, C.; Carry, B.; Hestroffer, D.; Merlin, F. (2011). "High-contrast observations of (136108) Haumea". Astronomy & Astrophysics 528: A105. arXiv:1101.2102. Bibcode:2011A&A...528A.105D. doi:10.1051/0004-6361/201015011.