moons of Haumea

Two small satellites were discovered around Haumea (which was at that time still designated 2003 EL₆₁) through observations using the W.M. Keck Observatory by a Caltech team in 2005.

The outer and larger of the two satellites was discovered 26 January 2005,{{cite journal

|author=M. E. Brown

|author-link=Michael E. Brown

|author2=A. H. Bouchez

|author3=D. Rabinowitz

|author4=R. Sari

|author5=C. A. Trujillo

|author6=M. van Dam

|author7=R. Campbell

|author8=J. Chin

|author9=S. Hardman

|author10=E. Johansson

|author11=R. Lafon

|author12=D. Le Mignant

|author13=P. Stomski

|author14=D. Summers

|author15=P. Wizinowich

|title=Keck Observatory Laser Guide Star Adaptive Optics Discovery and Characterization of a Satellite to the Large Kuiper Belt Object 2003 EL61

|journal=The Astrophysical Journal Letters

|volume=632|issue=1

|date=2005-09-02|pages=L45–L48

|bibcode=2005ApJ...632L..45B

|doi=10.1086/497641

|s2cid=119408563

|url=http://authors.library.caltech.edu/34486/1/1538-4357_632_1_L45.pdf

}} and formally designated S/2005 (2003 EL₆₁) 1, though nicknamed "Rudolph" by the Caltech team.{{cite news

|author=Kenneth Chang

|title=Piecing Together the Clues of an Old Collision, Iceball by Iceball

|url=https://www.nytimes.com/2007/03/20/science/space/20kuip.html

|work=New York Times

|date=2007-03-20

|access-date=2008-10-12

}} The smaller, inner satellite of Haumea was discovered on 30 June 2005, formally termed S/2005 (2003 EL₆₁) 2, and nicknamed "Blitzen". On 7 September 2006, both satellites were numbered and admitted into the official minor planet catalogue as (136108) 2003 EL₆₁ I and II, respectively.

The permanent names of these moons were announced, together with that of 2003 EL₆₁, by the International Astronomical Union on 17 September 2008: (136108) Haumea I Hi{{okina}}iaka and (136108) Haumea II Namaka.{{cite web

|title=News Release – IAU0807: IAU names fifth dwarf planet Haumea

|work=International Astronomical Union

|date=2008-09-17

|url=http://www.iau.org/public_press/news/release/iau0807/

|access-date=2008-09-18

}} Each moon was named after a daughter of Haumea, the Hawaiian goddess of fertility and childbirth. Hi{{okina}}iaka is the goddess of dance and patroness of the Big Island of Hawaii, where the Mauna Kea Observatory is located.{{cite news

|publisher=US Geological Survey Gazetteer of Planetary Nomenclature

|title=Dwarf Planets and their Systems

|url=http://planetarynames.wr.usgs.gov/append7.html#DwarfPlanets

|access-date=2008-09-17

}} Nāmaka is the goddess of water and the sea; she cooled her sister Pele's lava as it flowed into the sea, turning it into new land.

In her legend, Haumea's many children came from different parts of her body.{{cite book

|author=Robert D. Craig

|title=Handbook of Polynesian Mythology

|publisher=ABC-CLIO

|date=2004

|url=https://books.google.com/books?id=LOZuirJWXvUC&q=haumea&pg=PA128

|page=128

|isbn=1-57607-894-9

}} The dwarf planet Haumea appears to be almost entirely made of rock, with only a superficial layer of ice; most of the original icy mantle is thought to have been blasted off by the impact that spun Haumea into its current high speed of rotation, where the material formed into the small Kuiper belt objects in Haumea's collisional family. There could therefore be additional outer moons, smaller than Namaka, that have not yet been detected. However, HST observations have confirmed that no other moons brighter than 0.25% of the brightness of Haumea exist within the closest tenth of the distance (0.1% of the volume) where they could be held by Haumea's gravitational influence (its Hill sphere).{{cite journal

|last=Ragozzine |first=D.

|author2=Brown, M.E.

|date=2009

|title=Orbits and Masses of the Satellites of the Dwarf Planet Haumea = 2003 EL61

|journal=The Astronomical Journal

|arxiv=0903.4213

|bibcode = 2009AJ....137.4766R

|doi = 10.1088/0004-6256/137/6/4766

|volume=137

|issue=6

|pages=4766–4776

|s2cid=15310444

}} This makes it unlikely that any more exist.

File:Haumea Hubble.png image of Haumea (center), Hi{{okina}}iaka (above), and Namaka (below).]]

Hi{{okina}}iaka is the outer and, at roughly 310 km in diameter, the larger and brighter of the two moons.{{cite journal| doi = 10.1086/501524| last1 = Brown| first1 = M. E.| author-link = Michael E. Brown| last2 = Van Dam| first2 = M. A.| last3 = Bouchez| first3 = A. H.| last4 = Le Mignant| first4 = D.| last5 = Campbell| first5 = R. D.| last6 = Chin| first6 = J. C. Y.| last7 = Conrad| first7 = A.| last8 = Hartman| first8 = S. K.| last9 = Johansson| first9 = E. M.| last10 = Lafon| first10 = R. E.| last11 = Rabinowitz| first11 = D. L. Rabinowitz| last12 = Stomski| first12 = P. J. Jr.| last13 = Summers| first13 = D. M.| last14 = Trujillo| first14 = C. A.| last15 = Wizinowich| first15 = P. L.| year = 2006| title = Satellites of the Largest Kuiper Belt Objects| journal = The Astrophysical Journal| volume = 639| issue = 1| pages = L43–L46| arxiv = astro-ph/0510029| bibcode = 2006ApJ...639L..43B| s2cid = 2578831| url = http://web.gps.caltech.edu/~mbrown/papers/ps/gab.pdf| access-date = 19 October 2011| ref = {{sfnRef|Brown Van Dam et al.|2006}}

}} Strong absorption features observed at 1.5, 1.65 and 2 μm in its infrared spectrum are consistent with nearly pure crystalline water ice covering much of its surface. The unusual spectrum, and its similarity to absorption lines in the spectrum of Haumea, led Brown and colleagues to conclude that it was unlikely that the system of moons was formed by the gravitational capture of passing Kuiper belt objects into orbit around the dwarf planet: instead, the Haumean moons must be fragments of Haumea itself.{{cite web

|title=The largest Kuiper belt objects

|author=Michael E. Brown

|work=Caltech

|url=http://www.gps.caltech.edu/~mbrown/papers/ps/kbochap.pdf

|access-date=2008-09-19

}}

The sizes of both moons are calculated with the assumption that they have the same infrared albedo as Haumea, which is reasonable as their spectra show them to have the same surface composition. Haumea's albedo has been measured by the Spitzer Space Telescope: from ground-based telescopes, the moons are too small and close to Haumea to be seen independently. Based on this common albedo, the inner moon, Namaka, which is a tenth the mass of Hi{{okina}}iaka, would be about 170 km in diameter.{{cite web

|url=http://www.johnstonsarchive.net/astro/astmoons/am-136108.html

|title=(136108) Haumea, Hi'iaka, and Namaka

|publisher=Johnstonsarchive.net

|access-date=2009-02-01

}}

The Hubble Space Telescope (HST) has adequate angular resolution to separate the light from the moons from that of Haumea. Photometry of the Haumea triple system with HST's NICMOS camera has confirmed that the spectral line at 1.6 μm that indicates the presence of water ice is at least as strong in the moons' spectra as in Haumea's spectrum.{{cite journal

|last=Fraser |first=W.C.

|author2=Brown, M.E.

|date=2009

|title=NICMOS Photometry of the Unusual Dwarf Planet Haumea and its Satellites

|journal=The Astrophysical Journal Letters

|volume=695 |issue=1

|pages=L1–L3

|arxiv=0903.0860

|bibcode=2009ApJ...695L...1F

|doi=10.1088/0004-637X/695/1/L1

|s2cid=119273925

}}

The moons of Haumea are too faint to detect with telescopes smaller than about 2 metres in aperture, though Haumea itself has a visual magnitude of 17.5, making it the third-brightest object in the Kuiper belt after Pluto and Makemake, and easily observable with a large amateur telescope.

{{multiple image |direction=vertical |align=right |total_width=300

|image1=TheKuiperBelt Orbits Haumea moons.svg |caption1=A view of the orbits of Hi{{okina}}iaka (blue) and Namaka (green)

|image2=Haumea mutual events illustration.png |caption2=Illustration of mutual events between Haumea and Namaka during 2009–2011

}}

Hi{{okina}}iaka orbits Haumea nearly circularly every 49 days. Namaka orbits Haumea in 18 days in a moderately elliptical, non-Keplerian orbit, and as of 2008 was inclined 13° with respect to Hi{{okina}}iaka, which perturbs its orbit. Because the impact that created the moons of Haumea is thought to have occurred in the early history of the Solar System,{{cite journal

|author=Michael E. Brown |author2= Kristina M. Barkume |author3=Darin Ragozzine |author4=Emily L. Schaller

|date=2007-01-19

|title=A collisional family of icy objects in the Kuiper belt

|journal=Nature

|volume=446 |issue=7133 |pages=294–296

|doi=10.1038/nature05619

|pmid=17361177

|bibcode = 2007Natur.446..294B

|s2cid= 4430027 |url= https://authors.library.caltech.edu/34346/2/nature05619-s1.pdf }} over the following billions of years it should have been tidally damped into a more circular orbit. Namaka's orbit has likely been disturbed by orbital resonances with the more-massive Hi{{okina}}iaka due to converging orbits as they moved outward from Haumea due to tidal dissipation. They may have been caught in and then escaped from orbital resonance several times; they currently are in or at least close to an 8:3 resonance. This resonance strongly perturbs Namaka's orbit, which has a current precession of its argument of periapsis by about −6.5° per year, a precession period of 55 years.

From around 2008 to 2011,{{cite journal |last1=Dumas |first1=C. |last2=Carry |first2=B. |first3=D. |last3=Hestroffer |first4=F. |last4=Merlin |date=2011 |title=High-contrast observations of (136108) Haumea |url=https://www.aanda.org/articles/aa/full_html/2011/04/aa15011-10/aa15011-10.html |journal=Astronomy & Astrophysics |volume=528 |issue= |pages= A105|doi=10.1051/0004-6361/201015011 |access-date=24 August 2024|arxiv=1101.2102 |bibcode=2011A&A...528A.105D }} the orbits of the Haumean moons appeared almost exactly edge-on from Earth, with Namaka periodically occulting Haumea.{{cite web

|url = http://www.cfa.harvard.edu/~fabrycky/EL61/

|title = IAU Circular 8949

|date = 17 September 2008

|publisher = International Astronomical Union

|access-date = 2008-12-06

|url-status = dead

|archive-url = https://web.archive.org/web/20090111105134/http://www.cfa.harvard.edu/~fabrycky/EL61/

|archive-date = 11 January 2009

|df = dmy-all

}}{{cite web

|url=http://web.gps.caltech.edu/~mbrown/2003EL61/mutual/

|title=Mutual events of Haumea and Namaka

|author=Brown, M.

|access-date=2009-02-18

}} Observation of such transits would have provided precise information on the size and shape of Haumea and its moons, as happened in the late 1980s with Pluto and Charon.{{cite book

|author=Lucy-Ann Adams McFadden |author2=Paul Robert Weissman |author3=Torrence V. Johnson

|title=Encyclopedia of the Solar System

|url=https://books.google.com/books?id=G7UtYkLQoYoC&q=mutual+event+pluto&pg=PA545

|access-date=2008-10-17

|isbn=978-0-12-088589-3

|date=2007

|publisher=Elsevier }} The tiny change in brightness of the system during these occultations would have required at least a medium-aperture professional telescope for detection.{{cite journal |author=D. C. Fabrycky |display-authors=4 |author2=M. J. Holman |author3=D. Ragozzine |author4=M. E. Brown |author5=T. A. Lister |author6=D. M. Terndrup |author7=J. Djordjevic |author8=E. F. Young |author9=L. A. Young |author10=R. R. Howell |title=Mutual Events of 2003 EL61 and its Inner Satellite |pages=36.08 |journal=AAS DPS Conference 2008 |bibcode=2008DPS....40.3608F |year=2008 |volume=40 }} Hi{{okina}}iaka last occulted Haumea in 1999, a few years before discovery, and will not do so again for some 130 years.{{cite web

|title=Moon shadow Monday (fixed)

|author=Mike Brown

|date=2008-05-18

|publisher=Mike Brown's Planets

|url=http://www.mikebrownsplanets.com/2008/05/moon-shadow-monday-fixed.html

|access-date=2008-09-27

}} However, in a situation unique among regular satellites, Namaka's orbit was being greatly torqued by Hi{{okina}}iaka, which preserved the viewing angle of Namaka–Haumea transits for several more years.{{cite web

|author = D. Ragozzine

|author2 = M. E. Brown

|author3 = C. A. Trujillo

|author4 = E. L. Schaller

|title = Orbits and Masses of the 2003 EL61 Satellite System

|url = http://www.abstractsonline.com/viewer/viewAbstract.asp?CKey={421E1C09-F75A-4ED0-916C-8C0DDB81754D}&MKey={35A8F7D5-A145-4C52-8514-0B0340308E94}&AKey={AAF9AABA-B0FF-4235-8AEC-74F22FC76386}&SKey={545CAD5F-068B-4FFC-A6E2-1F2A0C6ED978}

|work = AAS DPS conference 2008

|access-date = 17 October 2008

|url-status = dead

|archive-url = https://web.archive.org/web/20130718182107/http://www.abstractsonline.com/viewer/viewAbstract.asp?CKey=%7B421E1C09-F75A-4ED0-916C-8C0DDB81754D%7D&MKey=%7B35A8F7D5-A145-4C52-8514-0B0340308E94%7D&AKey=%7BAAF9AABA-B0FF-4235-8AEC-74F22FC76386%7D&SKey=%7B545CAD5F-068B-4FFC-A6E2-1F2A0C6ED978%7D

|archive-date = 18 July 2013

|df = dmy-all

}} One occultation event was observed on 19 June 2009, from the Pico dos Dias Observatory in Brazil.{{cite journal |last1=Bortoletto |first1=A. |last2=Saito |first2=R. K. |date=2010 |title=Observing mutual events of the trans-Neptunian object Haumea and Namaka from Brazil |url=https://articles.adsabs.harvard.edu//full/2010IAUS..269..189B/0000189.000.html |journal=Proceedings of the International Astronomical Union |volume=269 |issue= |pages=189–192 |bibcode=2010IAUS..269..189B |doi= 10.1017/S1743921310007404|access-date=24 August 2024}}

class="wikitable" style="margin:1em auto;" border="1"
style="background:#efefef;" ! Label {{refn| group = note | Label refers to the Roman numeral attributed to each moon in order of their discovery.{{Cite web|title=Planet and Satellite Names and Discoverers|work=Gazetteer of Planetary Nomenclature|publisher=USGS Astrogeology|url=https://planetarynames.wr.usgs.gov/Page/Planets|access-date=2022-06-23}}}} ! colspan="2" | Name (pronunciation) ! Mean diameter (km) ! Mass (×1018 kg) ! Semi-major axis (km) ! Orbital period (days) ! Eccentricity ! Inclination (°){{refn | group = note |Orbital inclinations of Namaka and Hi{{okina}}iaka are with respect to Haumea's orbit.}} ! Discovery date
style="text-align:center; background:white;" | | colspan="2" | (ring)	≈ 70		{{val|2285|8}}	{{val|0.489438|0.000012}}{{cite journal|display-authors= 3|last1= Ortiz|first1=J. L.|last2= Santos-Sanz|first2=P.|last3= Sicardy|first3= B.|last4= Benedetti-Rossi|first4= G.|last5= Bérard|first5= D.|last6= Morales|first6= N.|last7= Duffard|first7= R.|last8= Braga-Ribas|first8=F.|last9= Hopp|first9=U.|last10= Ries|first10=C.|last11= Nascimbeni|first11=V.|last12= Marzari|first12=F.|last13= Granata|first13=V.|last14= Pál|first14=A.|last15= Kiss|first15=C.|last16= Pribulla|first16=T.|last17=Komžík|first17=R.|last18= Hornoch|first18=K.|last19=Pravec|first19=P.|last20= Bacci|first20=P.|last21= Maestripieri|first21= M.|last22= Nerli|first22=L.|last23=Mazzei|first23=L.|last24= Bachini|first24=M.|last25=Martinelli|first25= F.|last26=Succi|first26= G.|last27=Ciabattari|first27=F.|last28= Mikuz|first28=H.|last29=Carbognani|first29= A.|last30=Gaehrken|first30=B.|last31= Mottola|first31=S.|last32= Hellmich|first32=S.|last33=Rommel|first33=F. L.|last34=Fernández-Valenzuela|first34=E.|last35= Bagatin|first35=A. Campo|last36=Cikota|first36= S.|last37=Cikota|first37=A.|last38=Lecacheux|first38=J.|last39=Vieira-Martins|first39=R.|last40=Camargo|first40=J. I. B.|last41=Assafin|first41=M.|last42= Colas|first42=F.|last43=Behrend|first43= R.|last44=Desmars|first44=J.|last45=Meza|first45=E.|last46=Alvarez-Candal|first46=A.|last47=Beisker|first47=W.|last48= Gomes-Junior|first48=A. R.|last49= Morgado|first49=B. E.|last50=Roques|first50=F.|last51= Vachier|first51=F.|last52=Berthier|first52= J.|last53=Mueller|first53=T. G.|last54=Madiedo|first54=J. M.|last55=Unsalan|first55=O.|last56= Sonbas|first56=E.|last57=Karaman|first57= N.|last58=Erece|first58=O.|last59=Koseoglu|first59=D. T.|last60=Ozisik|first60=T.|last61= Kalkan|first61=S.|last62= Guney|first62=Y.|last63=Niaei|first63=M. S.|last64=Satir|first64=O.|last65= Yesilyaprak|first65=C.|last66= Puskullu|first66=C.|last67=Kabas|first67= A.|last68=Demircan|first68= O.|last69=Alikakos|first69=J.|last70= Charmandaris|first70=V.|last71=Leto|first71=G.|last72=Ohlert|first72=J.|last73=Christille|first73=J. M.|last74=Szakáts|first74=R.|last75=Farkas|first75=A. Takácsné|last76=Varga-Verebélyi|first76=E.|last77= Marton|first77=G.|last78=Marciniak|first78= A.|last79=Bartczak|first79=P.|last80=Santana-Ros|first80=T.|last81=Butkiewicz-Bąk|first81=M.|last82=Dudziński|first82=G.|last83=Alí-Lagoa|first83=V.|last84= Gazeas|first84=K.|last85= Tzouganatos|first85=L.|last86=Paschalis|first86=N.|last87=Tsamis|first87=V.|last88=Sánchez-Lavega|first88=A.|last89=Pérez-Hoyos|first89=S.|last90= Hueso|first90=R.|last91=Guirado|first91=J. C.|last92=Peris|first92=V.|last93=Iglesias-Marzoa|first93=R.|title=The size, shape, density and ring of the dwarf planet Haumea from a stellar occultation|journal= Nature|volume= 550|issue= 7675|year= 2017|pages= 219–223|doi= 10.1038/nature24051|pmid= 29022593|arxiv= 2006.03113|bibcode=2017Natur.550..219O|hdl= 10045/70230|s2cid= 205260767|hdl-access=free}}Based on a 3:1 resonance with Haumea's rotation period.		[approximately same as Haumea's equator]	January 2017
style="text-align:center; background:white;" | II	Namaka	{{IPA|/nɑːˈmɑːkə/}}	≈ 170?	{{val|1.79|1.48}} (≈ 0.05% Haumea)	{{val|25657|91}}	{{val|18.2783|0.0076}}Using Kepler's third law.	{{val|0.249|0.015}}As of 2008: Namaka's eccentricity and inclination are variable due to perturbation.	{{val|113.013|0.075}} ({{val|13.41|0.08}} from Hi{{okina}}iaka)	June 2005
style="text-align:center; background:white;" | I	Hi{{okina}}iaka	{{IPA|/hiːʔiːˈɑːkə/}}	≈ 310	{{val|17.9|1.1}} (≈ 0.5% Haumea)	{{val|49880|198}}	{{val|49.462|0.083}}	{{val|0.0513|0.0078}}	{{val|126.356|0.064}}	January 2005

{{reflist

| group = note

}}

{{notelist}}

{{Reflist|30em| refs =

{{Cite journal | last1 = Barkume | first1 = K. M. | last2 = Brown | first2 = M. E. | last3 = Schaller | first3 = E. L. | title = Water Ice on the Satellite of Kuiper Belt Object 2003 EL61 | doi = 10.1086/503159 | journal = The Astrophysical Journal | volume = 640 | issue = 1 | pages = L87–L89 | year = 2006 | url = http://www.gps.caltech.edu/~mbrown/papers/ps/rudolph.pdf|arxiv = astro-ph/0601534 |bibcode = 2006ApJ...640L..87B | s2cid = 17831967 }}

}}

• [https://web.archive.org/web/20090327050619/http://www.gps.caltech.edu/~darin/haumeasatsanim.gif Animation of the orbits of Haumea's moons]
• International Year of Astronomy 2009 [http://365daysofastronomy.org/2009/03/31/march-31st/ podcast: Dwarf Planet Haumea (Darin Ragozzine)]
• [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/~mbrown/papers/ps/rudolph.pdf Paper describing the composition of Hi{{okina}}iaka]

{{Moons of plutoids}}

{{Haumea}}

{{Solar System moons (compact)}}

{{Solar System}}

Category:Lists of moons

Category:Solar System