Hiʻiaka (moon)
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Hiʻiaka, formal designation (136108) Haumea I, is the larger, outer moon of the trans-Neptunian dwarf planet Haumea. It is named after one of the daughters of Haumea, Hiʻiaka, the patron goddess of the Big Island of Hawaii. It orbits once every Script error: No such module "val". at a distance of Script error: No such module "val"., with an eccentricity of Script error: No such module "val". and an inclination of Script error: No such module "val".. Assuming its estimated diameter of over 300 km is accurate, it may be the fourth- or fifth-largest known moon of a Trans-Neptunian object, after Pluto I Charon, Eris I Dysnomia, Orcus I Vanth, and possibly Varda I Ilmarë and Salacia I Actaea.
Discovery
Hiʻiaka was the first satellite discovered around Haumea. It was discovered on 26 January 2005 and nicknamed "Rudolph" by the discovery team before being assigned an official name.Script error: No such module "Unsubst".
Physical characteristics
Size and brightness
Stellar occultations by Hiʻiaka on 6 and 16 April 2021 reveal that the moon is elongated, with estimated ellipsoid dimensions of Template:Cvt.[1]Template:Rp These correspond to a volume-equivalent diameter of Template:Cvt.[1]Template:Rp To put this in perspective, if Hiʻiaka were in the asteroid belt, it would be larger than all but the four largest asteroids, after 1 Ceres, 2 Pallas, 4 Vesta, and 10 Hygiea. In spite of its relatively large size, Hiʻiaka is not in hydrostatic equilibrium because its elongated shape is inconsistent with that expected for its current rotation period.[1]Template:Rp
Mass and density
The mass of Hiʻiaka is estimated to be Script error: No such module "val". using precise relative astrometry from the Hubble Space Telescope and Keck Telescope and applying 3-body, point-mass model to the Haumean system.[2] Hiʻiaka's diameter and mass indicate it has a low density of Script error: No such module "val"., which suggests Hiʻiaka's interior consists of highly porous water ice with a rock mass fraction between 50% and 70%.[1]Template:Rp
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 Script error: No such module "val". 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.[3]
See also
- Namaka, the other moon of Haumea
References
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External links
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