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{{Short description|Larger moon of Haumea}} |
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{{Use dmy dates|date=July 2019}} |
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{{Infobox planet |
{{Infobox planet |
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| name = Hi{{okina}}iaka |
| name = Hi{{okina}}iaka |
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| image = Haumea-moons-hubble.gif |
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| bgcolour = #a0ffa0 |
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| caption = In this series of photos taken by the [[Hubble Space Telescope]], the brighter object Hi{{okina}}iaka is seen orbiting [[Haumea]] (center). |
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| image = [[Image:2003 EL61.jpg|275px]] |
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| discoverer = [[Michael E. Brown]], <br> [[Chad Trujillo]], <br> [[David Rabinowitz]], et al. |
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| caption = Hi{{okina}}iaka is above Haumea (center) in this [[Keck telescope]] image. |
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| discovery = yes |
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| discoverer = [[Michael E. Brown]],<br />[[Chad Trujillo]],<br />[[David Rabinowitz]], ''et al.'' |
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| discovered = 26 January 2005 |
| discovered = 26 January 2005 |
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| mpc_name = Haumea I |
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| alt_names = (136108) 2003 |
| alt_names = {{mp|(136108) 2003 EL|61}} I<br>{{mp|S|2005|2003 EL|61|1}} |
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| pronounced = {{IPAc-en|h|iː|ʔ|i|ˈ|ɑː|k|ə}}<br>{{IPA-haw|ˈhiʔiˈjɐkə|lang}} |
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| orbit_ref = <ref name= |
| orbit_ref = <ref name=RagozzineBrown2009/> |
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| semimajor = |
| semimajor = {{val|49880|198|ul=km}} |
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| eccentricity = 0.0513 |
| eccentricity = {{val|0.0513|0.0078}} |
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| period = 49.12 |
| period = {{val|49.12|0.03|u=days}} |
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| inclination = 126.356 |
| inclination = {{val|126.356|0.064|s=°}} |
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| asc_node = {{val|206.766|0.033|u=°}} |
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| arg_peri = {{val|154.1|5.8|u=°}} |
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| mean_anomaly = {{val|152.8|6.1|u=°}} |
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| satellite_of = {{dp|Haumea}} |
| satellite_of = {{dp|Haumea}} |
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| mean_radius = {{val|p=~|160|u=km}}<ref name=RagozzineBrown2009/> |
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| physical_characteristics = yes |
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| mass = {{val|1.79|0.11|e=19|ul=kg}}<ref name=RagozzineBrown2009/> (0.45% of Haumea) |
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| mean_radius = ~170 km<ref name=Dumas2011/> |
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| density = {{val|p=~|1|ul=g/cm3}} |
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| mass = 1.79 ± 0.11{{e|19}} [[Kilogram|kg]]<ref name="Ragozzine&Brown2009"/>(0.45% of Haumea) |
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| single_temperature = {{val|32|3|ul=K}} |
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| density = ~ 1 g/cm<sup>3</sup> |
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| rotation = {{val|9.8|u=h|p=~}}<ref name="Hastings2016"/> |
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| single_temperature = 32 ± 3 [[Kelvin|K]] |
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| axial_tilt = |
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| albedo = {{val|0.8|0.07}}<ref name=johnston/><ref name=RagozzineBrown2009/> |
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| axial_tilt = (unknown) |
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| magnitude = 20.3 (3.0 difference from primary's 17.3)<ref name=johnston/> |
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| albedo = (unknown) |
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| magnitude = 3.3 difference from primary's 17.3 |
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}} |
}} |
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'''Hi{{okina}}iaka''' is the larger, outer moon of the [[dwarf planet]] [[Haumea (dwarf planet)|Haumea]]. |
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'''Hi{{okina}}iaka''' is the larger, outer moon of the trans-Neptunian [[dwarf planet]] [[Haumea]]. It is named after one of the daughters of [[Haumea (mythology)|Haumea]], [[Hi{{okina}}iaka]], the patron goddess of the [[Big Island of Hawaii]]. It orbits once every {{val|49.12|0.03|u=days}} at a distance of {{val|49880|198|ul=km}}, with an eccentricity of {{val|0.0513|0.0078}} and an inclination of {{val|126.356|0.064|s=°}}. 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]]. |
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==Discovery and naming== |
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Hi{{okina}}iaka was the first [[natural satellite|satellite]] discovered around Haumea. It is named after one of the daughters of [[Haumea (mythology)|Haumea]], [[Hiiaka|Hi{{okina}}iaka]], the patron goddess of the [[Big Island of Hawaii]], though at first it had gone by the nickname "[[Rudolph the Red-Nosed Reindeer|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 Haumea system.<ref name="Ragozzine&Brown2009"/> |
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==Discovery== |
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==Physical characteristics== |
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Hi{{okina}}iaka was the first [[natural satellite|satellite]] discovered around Haumea. It was discovered on 26 January 2005 and nicknamed "[[Rudolph the Red-Nosed Reindeer|Rudolph]]" by the discovery team before being assigned an official name. |
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===Size and brightness=== |
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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.<ref name="Ragozzine&Brown2009"/> To put this in perspective, this moon would be the [[List_of_notable_asteroids#Largest_known_asteroids_.28out_to_the_orbit_of_Jupiter.29|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 Hi'iaka 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. |
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== Physical characteristics == |
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===Mass=== |
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The mass of Hi{{okina}}iaka is estimated to be 1.79 ± 0.11{{e|19}} [[Kilogram|kg]] using precise relative [[astrometry]] from [[Hubble Telescope]] and [[Keck Telescope]] and applying [[3-body problem|3-body]], point-mass model to the Haumea system.<ref name="Ragozzine&Brown2009"> |
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{{cite journal |
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|last=Ragozzine |
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|first=D. |
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|coauthors=Brown, M.E. |
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|year=2009 |
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|title=Orbits and Masses of the Satellites of the Dwarf Planet Haumea = 2003 EL61 |
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|journal=The Astronomical Journal |
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|id= |
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|arxiv=0903.4213|bibcode = 2009AJ....137.4766R |doi = 10.1088/0004-6256/137/6/4766 }} |
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</ref> |
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=== |
=== Size and brightness === |
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Its measured brightness is {{val|5.9|0.5|s=%}}, translating into a diameter of about 22% of its primary, or in the range of {{val|320|u=km}}, assuming similar infrared albedo.<ref name=RagozzineBrown2009/> To put this in perspective, if Hiʻiaka were in the asteroid belt, it would be larger than all but the [[List of notable asteroids#Largest by diameter|four]] largest asteroids, after [[1 Ceres]], [[2 Pallas]], [[4 Vesta]], and [[10 Hygiea]]. In spite of its relatively large size, however, lightcurve studies suggest that Hiʻiaka is not a gravitationally collapsed spheroid; they further suggest that Hiʻiaka is not tidally locked and has a rotation period of about 9.8 hours.<ref name="Hastings2016"/> |
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The near infrared spectrum of Hi'iaka 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 the [[amorphous]] form as would be expected due to its continues irradiation by [[cosmic ray]]s.<ref name=Dumas2011>{{cite doi|10.1051/0004-6361/201015011}}</ref> |
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=== Mass === |
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The mass of Hi{{okina}}iaka is estimated to be {{val|1.79|0.11|e=19|ul=kg}} using precise relative [[astrometry]] from the [[Hubble Space Telescope]] and [[Keck Telescope]] and applying [[3-body problem|3-body]], point-mass model to the Haumean system.<ref name=RagozzineBrown2009/> |
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=== Spectrum and composition === |
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The near infrared spectrum of Hi{{okina}}iaka 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 {{val|1.65|u=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 ray]]s.<ref name=Dumas2011/> |
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==See also== |
==See also== |
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*[[Moons of Haumea]] |
*[[Namaka (moon)|Namaka]], the other [[Moons of Haumea|moon of Haumea]] |
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==Notes== |
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{{reflist |
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| group = note |
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}} |
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{{notelist}} |
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==References== |
==References== |
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{{Reflist |
{{Reflist|30em| refs = |
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<ref name="RagozzineBrown2009"> |
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{{cite journal| doi = 10.1088/0004-6256/137/6/4766| last1 = Ragozzine| first1 = D.| last2 = Brown| first2 = M. E.| year = 2009| title = Orbits and Masses of the Satellites of the Dwarf Planet Haumea (2003 EL61)| journal = The Astronomical Journal| volume = 137| issue = 6| pages = 4766–4776| arxiv = 0903.4213| bibcode = 2009AJ....137.4766R| s2cid = 15310444}} |
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</ref> |
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<ref name="Dumas2011">{{Cite journal | last1 = Dumas | first1 = C.| last2 = Carry | first2 = B.| last3 = Hestroffer | first3 = D.| last4 = Merlin | first4 = F.| title = High-contrast observations of (136108) Haumea | doi = 10.1051/0004-6361/201015011 | journal = Astronomy & Astrophysics | volume = 528 | pages = A105 | year = 2011 |bibcode = 2011A&A...528A.105D |arxiv = 1101.2102 | s2cid = 119226136}}</ref> |
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<ref name=johnston> |
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{{cite web |
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| url = http://www.johnstonsarchive.net/astro/astmoons/am-136108.html |
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| author = Wm. Robert Johnston |
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| title = (136108) Haumea, Hiʻiaka, and Nāmaka |
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| date = 17 September 2008 |
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| access-date = 2008-09-18 |
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}} |
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</ref> |
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<ref name="Hastings2016">{{cite journal |
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|title = The Short Rotation Period of Hiʻiaka, Haumea's Largest Satellite |
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|last1 = Hastings |first1 = Danielle M. |
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|last2 = Ragozzine |first2 = Darin |
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|last3 = Fabrycky |first3 = Daniel C. |
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|last4 = Burkhart |first4 = Luke D. |
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|last5 = Fuentes |first5 = Cesar |
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|last6 = Margot |first6 = Jean-Luc |
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|last7 = Brown |first7 = Michael E. |
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|last8 = Holman |first8 = Matthew |
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|date = December 2016 |
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|journal = The Astronomical Journal |
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|volume = 152 |
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|issue = 6 |
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|id = 195 |
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|pages = 12 |
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|doi = 10.3847/0004-6256/152/6/195 |
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|arxiv = 1610.04305 |
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|bibcode = 2016AJ....152..195H |
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|oclc = 6889796157 |
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|osti = 22662917|s2cid = 33292771 |doi-access = free }}</ref> |
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}} |
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==External links== |
==External links== |
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*[http://www.gps.caltech.edu/%7Embrown/papers/ps/EL61.pdf Brown's publication describing the discovery of Hi{{okina}}iaka] |
* [http://www.gps.caltech.edu/%7Embrown/papers/ps/EL61.pdf Brown's publication describing the discovery of Hi{{okina}}iaka] |
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*[http://www.gps.caltech.edu/~mbrown/papers/ps/rudolph.pdf Paper describing the composition of Hi{{okina}}iaka] |
* [http://www.gps.caltech.edu/~mbrown/papers/ps/rudolph.pdf Paper describing the composition of Hi{{okina}}iaka] |
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{{Moons of plutoids}} |
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{{Haumea}} |
{{Haumea}} |
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{{ |
{{Solar System moons (compact)}} |
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{{Trans-Neptunian objects}} |
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{{Use dmy dates|date=September 2010}} |
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{{DEFAULTSORT:Hi'iaka ( |
{{DEFAULTSORT:Hi'iaka (moon)}} |
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[[Category: |
[[Category:Moons of Haumea]] |
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[[Category:Trans-Neptunian satellites]] |
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[[Category:Discoveries by Michael E. Brown]] |
[[Category:Discoveries by Michael E. Brown]] |
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[[Category:Discoveries by Chad Trujillo]] |
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[[Category:Discoveries by David L. Rabinowitz]] |
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[[bg:Хияка (спътник)]] |
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[[Category:Objects observed by stellar occultation]] |
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[[de:Hiʻiaka (Mond)]] |
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[[el:Χιιάκα (δορυφόρος)]] |
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[[es:Hiʻiaka (satélite)]] |
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[[fr:Hiʻiaka (lune)]] |
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[[gl:Hi'iaka (lúa)]] |
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[[ko:히이아카 (위성)]] |
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[[it:Hi'iaka]] |
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[[nl:Hi'iaka]] |
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[[ja:ヒイアカ (衛星)]] |
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[[nds:Hi’iaka (Maand)]] |
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[[pl:Hi'iaka (księżyc)]] |
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[[pt:Hiʻiaka]] |
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[[sk:Hi'iaka]] |
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[[sl:Hi'iaka (luna)]] |
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[[sv:Hiʻiaka]] |
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[[zh-yue:妊衛一]] |
![]()
In this series of photos taken by the Hubble Space Telescope, the brighter object Hiʻiaka is seen orbiting Haumea (center).
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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 |
Designations | |
Designation | Haumea I |
Pronunciation | /hiːʔiˈɑːkə/ Hawaiian: [ˈhiʔiˈjɐkə] |
(136108) 2003 EL61 I S/2005 (2003 EL61) 1 | |
Orbital characteristics[1] | |
49880±198 km | |
Eccentricity | 0.0513±0.0078 |
49.12±0.03 d | |
152.8°±6.1° | |
Inclination | 126.356±0.064° |
206.766°±0.033° | |
154.1°±5.8° | |
Satellite of | Haumea |
Physical characteristics | |
Mean radius | ~160 km[1] |
Mass | (1.79±0.11)×1019 kg[1] (0.45% of Haumea) |
Mean density | ~1 g/cm3 |
~9.8 h[2] | |
Albedo | 0.8±0.07[3][1] |
Temperature | 32±3 K |
20.3 (3.0 difference from primary's 17.3)[3] | |
Hiʻiaka 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 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°. 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.
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.
Its measured brightness is 5.9±0.5%, translating into a diameter of about 22% of its primary, or in the range of 320 km, assuming similar infrared albedo.[1] 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, however, lightcurve studies suggest that Hiʻiaka is not a gravitationally collapsed spheroid; they further suggest that Hiʻiaka is not tidally locked and has a rotation period of about 9.8 hours.[2]
The mass of Hiʻiaka is estimated to be (1.79±0.11)×1019 kg using precise relative astrometry from the Hubble Space Telescope and Keck Telescope and applying 3-body, point-mass model to the Haumean system.[1]
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.[4]
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Moons and rings |
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Astronomy |
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Natural satellites of the Solar System
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Planetary satellitesof |
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Dwarf planet satellitesof |
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Minor-planet moons |
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Ranked by size |
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