Hi'iaka (moon)
Hiʻiaka is above Haumea (center) in this Keck telescope image.
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Discovery
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| Discovered by | Michael E. Brown, Chad Trujillo, David Rabinowitz, et al. |
| Discovery date | 26 January 2005 |
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Designations
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| MPC designation | Haumea I Hiʻiaka |
| Pronunciation | /ˌhiːʔiˈɑːkə/,[1] or as in Hawaiian [ˈhiʔiˈjɐkə] |
| Alternate name(s) | (136108) 2003 EL61 I, S/2005 (2003 EL61) 1 |
| Semi-major axis | 49,880±198 km |
| Eccentricity | 0.0513±0.0078 |
| Orbital period | 49.12±0.03 days |
| Inclination | 126.356±0.064° |
| Satellite of | Haumea |
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Physical characteristics
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| Mean radius | ~170 km[3] |
| Mass | 1.79±0.11×1019 kg[2](0.45% of Haumea) |
| Mean density | ~1 g/cm3 |
| Rotation period | (unknown) |
| Axial tilt | (unknown) |
| Albedo | (unknown) |
| Temperature | 32±3 K |
| Apparent magnitude | 3.3 difference from primary's 17.3 |
Hiʻiaka is the larger, outer moon of the dwarf planet Haumea.
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[edit] 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 days at a distance of 49,880±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.[2]
[edit] Physical characteristics
[edit] Size and brightness
Its measured brightness is 5.9±0.5%, translating into the diameter about 22% of its primary, or in the range of 350 km, assuming similar albedo.[2] To put this in perspective, this moon would be the fifth largest (cis-neptunian) asteroid after 1 Ceres, 2 Pallas, 4 Vesta, and 10 Hygiea if it were in the asteroid belt. Future exploration of Haumea and its moons could reveal that Hiʻiaka is rounded by its own gravity, in other words is in hydrostatic equilibrium. However, it would not be a potential dwarf-planet candidate because, like Namaka, it is a moon.
[edit] Mass
The mass of Hiʻiaka is estimated to be 1.79±0.11×1019 kg using precise relative astrometry from Hubble Telescope and Keck Telescope and applying 3-body, point-mass model to the Haumean system.[2]
[edit] Spectrum and composition
The near infrared spectrum of Hiʻiaka is dominated by water-ice absorption bands, which means that the surface of this moon is made mainly of water ice. The presence of the band centered at 1.65 µm indicates that the 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]
[edit] See also
[edit] References
- ^ In US dictionary transcription, US dict: hē′·-ē·â′·kə.
- ^ a b c d e 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.
- ^ a b Dumas, C.; Carry, B.; Hestroffer, D.; Merlin, F. (2011). "High-contrast observations of (136108) Haumea". Astronomy & Astrophysics 528: A105. doi:10.1051/0004-6361/201015011.
[edit] External links
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