View source for Himalia (moon)

{{short description|Moon of Jupiter (Jupiter VI)}}
{{Use dmy dates|date=November 2020}}
{{about|Jupiter's irregular moon|the mythological figure|Himalia (mythology)}}
{{Infobox planet
| name = Himalia
| image = Himalia.png
| image_scale = 
| caption = Low-resolution image of Himalia from ''[[Cassini–Huygens|Cassini]]'', December 2000
| pronounced = {{IPAc-en|h|ɪ|ˈ|m|eɪ|l|i|ə}} or {{IPAc-en|h|ɪ|ˈ|m|ɑː|l|i|ə}}<ref>Daintith & Gould (2006) ''The Facts on File Dictionary of Astronomy'', p. 216</ref>
| adjectives = Himalian<ref>Yenne (1987) ''The Atlas of the Solar System''.</ref>
| named_after = [[Himalia (mythology)|Ἱμαλία]] ''Himalia''
| mpc_name = Jupiter VI
| alt_names = 
| discovery_ref = <ref name="Discovery"/>
| discoverer = [[Charles Dillon Perrine|Charles D. Perrine]]
| discovery_site = [[Lick Observatory]]
| discovered = 3 December 1904
| earliest_precovery_date = 
| satellite_of = [[Jupiter]]
| group = [[Himalia group]]
| orbit_ref = <ref name="MPC115889"/>
| epoch = 27 April 2019 ([[Julian day|JD]] 2458600.5)
| observation_arc = 114.25 [[Julian year (astronomy)|yr]] (41,728 days)
| semimajor = {{cvt|0.0761287|AU|km|lk=in}}
| eccentricity = 0.1537860
| period = +248.29 d
| mean_anomaly = 94.30785[[Degree (angle)|°]]
| mean_motion = {{Deg2DMS|1.44989322|sup=ms}} / day
| inclination = 29.90917° {{small|(to the [[ecliptic]])}}
| asc_node = 44.99935°
| arg_peri = 21.60643°
| dimensions = 205.6 × 141.3 km {{small|(occultation, projected)}}<ref name="occultation"/><br />{{val|150|20}}&thinsp;×&thinsp;{{val|120|20}} km (''Cassini'' estimate)<ref name="Porco2003"/>
| mean_diameter = {{val|139.6|1.7|u=km}}<ref name="Grav2015"/>
| surface_area = 
| volume = 
| mass = {{val|4.2|0.6|e=18|ul=kg}}<ref name="Emelyanov2005" />
| density = {{val|1.63|u=g/cm3}} (assuming radius 85&nbsp;km)<ref name="Emelyanov2005" />{{efn|name=lowden|1=Density = GM / [[Gravitational constant|G]] / ([[Volume#Formulas|Volume of a sphere]] of 85km) = 1.63 [[Gram|g]]/[[Cubic centimeter|cm<sup>3</sup>]]}}
| surface_grav = ~&thinsp;0.062 [[Acceleration|m/s<sup>2</sup>]] (0.006 g)
| escape_velocity = ~&thinsp;0.100 km/s
| rotation = {{val|7.7819|0.0005|ul=h}}<ref name="Pilcher2012"/>
| albedo = {{val|0.057|0.008}}<ref name="Grav2015"/>
| magnitude = 14.6<ref name="jplssd"/>
| abs_magnitude = 7.9<ref name="MPC115889"/>
| spectral_type = [[C-type asteroid|C]]<ref name="Grav2015"/>
}}

'''Himalia''' ({{IPAc-en|h|ɪ|ˈ|m|eɪ|l|i|ə|,_|h|ɪ|ˈ|m|ɑː|l|i|ə}}), also known as '''Jupiter VI''', is the largest [[irregular satellite]] of [[Jupiter]]. With a diameter of at least {{convert|140|km|mi|sigfig=1|abbr=on}},<ref name="occultation"/> it is the sixth largest [[Moons of Jupiter|Jovian satellite]], after the four [[Galilean moons]] and [[Amalthea (moon)|Amalthea]]. It was discovered by [[Charles Dillon Perrine]] at the [[Lick Observatory]] on 3 December 1904 and is named after the [[nymph]] [[Himalia (mythology)|Himalia]], who bore three sons of [[Zeus]] (the Greek equivalent of Jupiter).<ref name="Discovery" /> It is one of the largest planetary moons in the Solar System not imaged in detail, and the third largest not imaged in detail within the orbit of [[Neptune]].{{efn|It is the largest with the exception of [[Sycorax (moon)|Sycorax]] and [[Puck (moon)|Puck]] orbiting Uranus, some of the [[moons of Neptune]] and several trans-Neptunian objects, particularly [[Dysnomia (moon)|Dysnomia]], the moon of {{dp|Eris}}. [[List of natural satellites]]}}

== Discovery ==
Himalia was discovered by [[Charles Dillon Perrine]] at the [[Lick Observatory]] on 3 December 1904 in photographs taken with the 36-inch Crossley reflecting telescope which he had recently rebuilt.<ref name="Discovery">
{{cite journal|title=Discovery of a Sixth Satellite of Jupiter |journal=Astronomical Journal |volume=24 |issue=18 |date=1905 |pages=154B |bibcode = 1905AJ.....24..154P |doi = 10.1086/103612 |last1=Porter |first1=J.G.|doi-access=free }}; <br />
{{cite journal|title=Sixth Satellite of Jupiter Confirmed |journal=Harvard College Observatory Bulletin |volume=175 |date=1905-01-25 |page=1 |bibcode = 1905BHarO.175....1P |last1=Perrine |first1=C.D.}}; <br />
{{cite journal|last=Perrine|first=C.D. |title=Discovery of a Sixth Satellite to Jupiter |journal=Publications of the Astronomical Society of the Pacific |volume=17 |issue=100 |date=1905 |pages=22–23 |doi=10.1086/121619 |bibcode=1905PASP...17...22.|doi-access=free }}; <br />
{{cite journal|last=Perrine|first=C.D. |title=Orbits of the sixth and seventh satellites of Jupiter |journal=Astronomische Nachrichten |volume=169 |date=1905 |issue=3 |pages=43–44 |doi=10.1002/asna.19051690304 |bibcode=1905AN....169...43P|url=https://zenodo.org/record/1424813 }}
</ref> Himalia is Jupiter's most easily observed small satellite; though [[Amalthea (moon)|Amalthea]] is brighter, its proximity to the planet's brilliant disk makes it a far more difficult object to view.<ref>{{cite web |url=http://www.biophysik.uni-freiburg.de/Reiner/ATM/artikel/Himalia_e.html |title=Himalia, Jupiter's "fifth" moon |date=October 2009 |archive-url=https://web.archive.org/web/20110719102944/http://www.biophysik.uni-freiburg.de/Reiner/ATM/artikel/Himalia_e.html | archive-date = July 19, 2011}}</ref><ref>{{cite web |url=http://www.astronomy.net/articles/18/ |title=Finding Himalia, The Fifth Brightest Moon Of Jupiter |author=Rick Scott |website=Astronomy.net |date=October 20, 2003 |access-date=2011-11-07}}</ref>

=== Name ===
Himalia is named after the [[nymph]] [[Himalia (mythology)|Himalia]], who bore three sons of [[Zeus]] (the Greek equivalent of Jupiter). The moon did not receive its present name until 1975;<ref name="IAUC 2846">{{cite web |last=Marsden |first=B. G. |title=IAUC 2846: N Mon 1975 (= A0620-00); N Cyg 1975; 1975h; 1975g; 1975i; Sats OF JUPITER |website=Central Bureau for Astronomical Telegrams |date=7 October 1975 |publisher=[[IAU]] |url=http://www.cbat.eps.harvard.edu/iauc/02800/02846.html |access-date=2018-09-09}}</ref> before then, it was simply known as '''{{nowrap|Jupiter VI}}''' or '''Jupiter Satellite VI''', although calls for a full name appeared shortly after its and [[Elara (moon)|Elara]]'s discovery; A.C.D. Crommelin wrote in 1905:
{{cquote|Unfortunately the numeration of Jupiter's satellites is now in precisely the same confusion as that of Saturn's system was before the numbers were abandoned and names substituted. A similar course would seem to be advisable here; the designation V for the inner satellite [Amalthea] was tolerated for a time, as it was considered to be in a class by itself; but it has now got companions, so that this subterfuge disappears. The substitution of names for numerals is certainly more poetic.<ref name="Crommelin">{{cite journal|last=Crommelin|first=A. C. D.| bibcode=1905MNRAS..65..524C|title=Provisional Elements of Jupiter's Satellite VI|journal=[[Monthly Notices of the Royal Astronomical Society]]|volume=65|issue=5|pages=524–527|date=March 10, 1905|doi=10.1093/mnras/65.5.524|doi-access=free}}</ref>}}

The moon was sometimes called '''Hestia''', after the [[Hestia|Greek goddess]], from 1955 to 1975.<ref name="Gaposchkin">{{cite book| last=Payne-Gaposchkin|first=Cecilia|author2=Katherine Haramundanis|title=Introduction to Astronomy|date=1970|publisher=[[Prentice-Hall]]|location=Englewood Cliffs, N.J.|isbn=978-0-13-478107-5}}</ref>

== Orbit ==
[[File:Animation of Himalia orbit around Jupiter.gif|thumb|upright|left|Animation of Himalia's orbit.<br />{{legend2|RoyalBlue| Jupiter}}{{·}}{{legend2| Magenta | Himalia}}{{·}}{{legend2|Cyan|Callisto}}]]

At a distance of about {{convert|11400000|km|mi|abbr=on}} from Jupiter, Himalia takes about 250 [[Earth]] [[day]]s to complete one orbit around Jupiter.<ref>{{cite web |title=Himalia |url=https://solarsystem.nasa.gov/moons/jupiter-moons/himalia/in-depth/ |date=December 5, 2017 |website=Solar System Exploration |publisher=[[NASA]] |access-date=2018-09-09}}</ref> It is the largest member of the [[Himalia group]], which are a group of small moons orbiting Jupiter at a distance from {{convert|11400000|km|mi|abbr=on}} to {{convert|13000000|km|mi|abbr=on}}, with inclined orbits at an angle of 27.5 degrees to Jupiter's [[equator]].<ref name=Jewitt2004>{{cite book |last=Jewitt |first=David C. |author2=Sheppard, Scott |author3=Porco, Carolyn |name-list-style=amp |chapter=Jupiter's Outer Satellites and Trojans |title=Jupiter: The planet, Satellites and Magnetosphere |date=2004 |publisher=[[Cambridge University Press]] |editor=Bagenal, Fran |editor2=Dowling, Timothy E. |editor3=McKinnon, William B. |chapter-url=http://www.dtm.ciw.edu/users/sheppard/pub/Sheppard04JupChapter.pdf }}</ref> Their orbits are continuously changing due to solar and planetary perturbations.<ref name="Jacobson2000">{{cite journal | last = Jacobson | first = R. A. | title = The orbits of outer Jovian satellites |journal = Astronomical Journal | date = 2000 | volume = 120 | issue = 5 | pages = 2679–2686 | doi = 10.1086/316817 | bibcode = 2000AJ....120.2679J | s2cid = 120372170 | url = https://trs.jpl.nasa.gov/bitstream/2014/15175/1/00-1187.pdf }}</ref>

== Physical characteristics ==
[[File:Himalia Lightcurve2010.png|thumb|upright|left|Himalia's rotational [[light curve]] from Earth-based observations taken between August and October 2010.<ref name="Pilcher2012" />]]
[[File:Himalia-WISE.gif|thumb|upright|Himalia observed by the [[Wide-field Infrared Survey Explorer]] (WISE) spacecraft in 2014]]
Himalia's [[rotation period|rotational period]] is {{val|7|u=h}} {{val|46|u=m}} {{val|55|2|u=s}}.<ref name="Pilcher2012" /> Himalia appears neutral in color (grey), like the other members of its group, with [[colour index|colour indices]] B−V=0.62, V−R=0.4, similar to a [[C-type asteroid]].<ref name="RettigWalshConsolmagno2001" /> Measurements by ''Cassini'' confirm a featureless [[electromagnetic spectrum|spectrum]], with a slight absorption at {{val|3|u=μm}}, which could indicate the presence of water.<ref name="Chamberlain">{{cite journal|last=Chamberlain|first=Matthew A.|author2=Brown, Robert H.| title=Near-infrared spectroscopy of Himalia |journal=Icarus |volume=172|date=2004 |issue=1 |pages=163–169 |doi=10.1016/j.icarus.2003.12.016 |bibcode=2004Icar..172..163C}}</ref>
Although Himalia is the sixth-largest moon of Jupiter, it is the fifth-most massive. [[Amalthea (moon)|Amalthea]] is only a few km bigger, but less massive.
Resolved images of Himalia by ''Cassini'' have led to a size estimate of {{convert|150|x|120|km|mi|abbr=on}}, while ground-based estimates suggest that Himalia is large, with a diameter around {{convert|170|km|mi|abbr=on}}.<ref name="Porco2003"/><ref name="jplssd"/> In May 2018, Himalia [[occulted]] a star, allowing for precise measurements of its size.<ref name="occultation"/> The occultation was observed from the [[United States|US]] state of [[Georgia (U.S. state)|Georgia]].<ref name="occultation"/> From the occultation, Himalia was given a size estimate of {{convert|205.6|x|141.3|km|mi|abbr=on}}, in agreement with earlier ground-based estimates.<ref name="occultation"/>

=== Mass ===
In 2005, Emelyanov estimated Himalia to have a mass of {{val|4.2|0.6|e=18|ul=kg}} ([[Standard_gravitational_parameter|GM]]=0.28±0.04), based on a [[Perturbation (astronomy)|perturbation]] of [[Elara (moon)|Elara]] on July 15, 1949 (when the distance between them became a mere 64246.04 kilometers).<ref name="Emelyanov2005">{{cite journal
  | last = Emelyanov | first = N.V.
  | title=The mass of Himalia from the perturbations on other satellites
  | journal=Astronomy and Astrophysics
  | volume=438
  | issue=3 |pages=L33–L36 |date=2005
  | doi=10.1051/0004-6361:200500143 |bibcode=2005A&A...438L..33E
  | url=https://www.aanda.org/articles/aa/pdf/2005/30/aahe201.pdf | doi-access=free
  }}</ref> JPL's Solar System dynamics website assumes that Himalia has a mass of {{val|2.3|e=18|u=kg}} (GM=0.15) with a radius of {{val|85|u=km}}.<ref name="jplssd" />

Himalia's density will depend on whether it has an average radius of about {{val|67|u=km}} ([[geometric mean]] from ''Cassini'')<ref name=Emelyanov2005/> or a radius closer to {{val|85|u=km}}.<ref name="jplssd" />
[[File:Cassini-Huygens Image of Himalia.png|thumb|upright|left|''Cassini'' image of Himalia, taken in December 2000 from a distance of 4.4 million kilometres]]
{| class=wikitable
|-
! Source !! Radius <br /> km!!Density <br /> [[Gram|g]]/[[Cubic centimeter|cm<sup>3</sup>]] !! Mass <br /> [[Kilogram|kg]]
|-
| Emelyanov || [[geometric mean|67]] || 3.33 || 4.2{{e|18}}
|-
| Emelyanov || 85 || 1.63{{efn|name=lowden}} || 4.2{{e|18}}
|-
| JPL SSD || 85 || 0.88 || 2.3{{e|18}}
|}

== Exploration ==
[[File:Himalia - New Horizons.png|thumb|Phases of Himalia imaged by the LORRI instrument aboard ''New Horizons'']]
In November 2000, the ''[[Cassini–Huygens|Cassini]]'' spacecraft, en route to [[Saturn]], made a number of images of Himalia, including photos from a distance of 4.4&nbsp;million&nbsp;km. Himalia covers only a few pixels, but seems to be an elongated object with axes {{val|150|20}} and {{val|120|20|u=km}}, close to the Earth-based estimations.<ref name="Porco2003" />

In February and March 2007, the ''[[New Horizons]]'' spacecraft en route to Pluto made a series of images of Himalia, culminating in photos from a distance of 8&nbsp;million&nbsp;km. Again, Himalia appears only a few pixels across.<ref name="PlanetarySoc" />

== Himalia ring ==
[[File:Himalia ring.jpg|thumb|upright|Composite of six ''New Horizons'' images of the possible Himalia ring. The double exposure of Himalia is circled. The arrow points to Jupiter.]]
In September 2006, as NASA's ''[[New Horizons]]'' mission to [[Pluto]] approached Jupiter for a [[gravity assist]], it photographed what appeared to be a faint new [[rings of Jupiter|planetary ring]] parallel with and slightly inside Himalia's orbit. Because the small (4-km) moon [[Dia (moon)|Dia]], which had a similar orbit to Himalia, had gone missing since its discovery in 2000, there was some speculation that the ring could be debris from an impact of Dia into Himalia, suggesting that Jupiter continued to gain and lose small moons through collisions.<ref name="HimaliaRing">{{cite web |url=https://www.newscientist.com/article/mg20527523.400-lunar-marriage-may-have-given-jupiter-a-ring.html |title=Lunar marriage may have given Jupiter a ring |work=[[New Scientist]] |date=March 20, 2010 |page=16}}</ref>
However, an impact by an object the size of Dia would produce far more material than the calculated amount of ejected material needed to form the ring, although it is possible that a smaller, unknown moon may have been involved instead.<ref name="Cheng2010">{{cite conference
|title = A New Ring or Ring Arc of Jupiter?
|url = https://www.lpi.usra.edu/meetings/lpsc2010/pdf/2549.pdf
|first1 = A. F. |last1 = Cheng
|first2 = H. A. |last2 = Weaver
|first3 = L. |last3 = Nguyen
|first4 = D. P. |last4 = Hamilton
|first5 = S. A. |last5 = Stern
|first6 = H. B. |last6 = Throop
|date = March 2010
|conference = 41st Lunar and Planetary Science Conference
|publisher = Lunar and Planetary Institute
|number = 1533
|page = 2549
|bibcode = 2010LPI....41.2549C}}</ref>
The recovery of Dia in 2010 and 2011 disproved any connection between Dia and the Himalia ring.<ref name="MPEC2012-R22">{{cite web
  |date=2012-09-11
  |title=MPEC 2012-R22 : S/2000 J 11
  |publisher=[[Minor Planet Center]]
  |author=Gareth V. Williams
  |url=http://www.minorplanetcenter.net/mpec/K12/K12R22.html
|url-status=dead |archive-url=https://web.archive.org/web/20140821040352/http://www.minorplanetcenter.net/mpec/K12/K12R22.html |archive-date=2014-08-21
  |access-date=2012-09-11}}</ref><ref>
{{cite web |url=https://dtm.carnegiescience.edu/news/long-lost-moon-jupiter-found |title=Long Lost Moon of Jupiter Found |date=May 13, 2013 |website=Carnegie Science {{!}} DTM |access-date=2018-09-09}}
</ref>

== Notes ==
{{notelist}}

== See also ==
* [[Moons of Jupiter]]


== References ==
{{reflist
| refs =

<ref name="RettigWalshConsolmagno2001">
{{cite journal| doi = 10.1006/icar.2001.6715| last1 = Rettig | first1 = T. W.| last2 = Walsh | first2 = K.| last3 = Consolmagno | first3 = G.| author-link3 = Guy Consolmagno| date=December 2001 | title = Implied Evolutionary Differences of the Jovian Irregular Satellites from a BVR Color Survey| journal = Icarus| volume = 154| issue = 2| pages = 313–320| bibcode = 2001Icar..154..313R}}
</ref>

<ref name="PlanetarySoc">
{{cite web|url=http://www.planetary.org/multimedia/space-images/jupiter/himalia.html|title=The Bruce Murray Space Image Library – Jupiter's moon Himalia|author=Lakdawalla, E.|date=1 March 2007|access-date=17 November 2018}}
</ref>

<ref name="MPC115889">
{{cite web|url=https://minorplanetcenter.net/iau/ECS/MPCArchive/2019/MPC_20190827.pdf|title=M.P.C. 115889|work=Minor Planet Circular|publisher=Minor Planet Center|date=27 August 2019|access-date=27 February 2020}}
</ref>

<ref name="Grav2015">{{cite journal
  |display-authors = etal
  |first1     = T. |last1 = Grav
  |first2     = J. M. |last2 = Bauer
  |first3     = A. K. |last3 = Mainzer
  |first4     = J. R. |last4 = Masiero
  |first5     = C. R. |last5 = Nugent
  |first6     = R. M. |last6 = Cutri
  |date       = August 2015
  |title      = NEOWISE: Observations of the Irregular Satellites of Jupiter and Saturn
  |journal    = The Astrophysical Journal
  |volume     = 809
  |issue      = 1
  |id         = 3
  |pages      = 9
  |doi        = 10.1088/0004-637X/809/1/3
  |arxiv = 1505.07820 |bibcode    = 2015ApJ...809....3G|s2cid = 5834661 }}</ref>

<ref name="jplssd">{{cite web
  | title=Planetary Satellite Physical Parameters
  | url=https://ssd.jpl.nasa.gov/sats/phys_par/
  | publisher=Jet Propulsion Laboratory
  | accessdate=2022-03-28 }}</ref>

<ref name="Porco2003">{{cite journal | last = Porco | first = Carolyn C. |display-authors=etal | title = Cassini Imaging of Jupiter's Atmosphere, Satellites, and Rings | url = https://www.researchgate.net/publication/10867818 | journal = Science | volume = 299 |date=March 2003 | pages = 1541–1547 | doi = 10.1126/science.1079462 | pmid = 12624258 | issue = 5612 | bibcode = 2003Sci...299.1541P | s2cid = 20150275 }}</ref>

<ref name="Pilcher2012">{{cite journal | last = Pilcher | first = Frederick | author2=Mottola, Stefano | author3=Denk, Tilmann | title = Photometric lightcurve and rotation period of Himalia (Jupiter VI) |journal = Icarus | date = 2012 | volume = 219 | issue = 2 | pages = 741–742 | doi = 10.1016/j.icarus.2012.03.021 |bibcode = 2012Icar..219..741P }}</ref>

<ref name="occultation">{{cite web |url=http://www.asteroidoccultation.com/observations/Results/Data2018/20180512%20P5M06%20HimaliaProfile.gif |website=www.asteroidoccultation.com |title=Jupiter (06) Himalia |author1=N. Smith |author2=R. Venable |date=12 May 2018 |access-date=23 July 2018|url-status=dead|archive-url=https://web.archive.org/web/20180724032301/http://www.asteroidoccultation.com/observations/Results/Data2018/20180512%20P5M06%20HimaliaProfile.gif|archive-date=24 July 2018}}</ref>

}}

== External links ==
* [https://web.archive.org/web/20160411155354/http://solarsystem.nasa.gov/planets/himalia "Himalia: Overview"] by [http://solarsystem.nasa.gov NASA's Solar System Exploration]
* [https://web.archive.org/web/20060901072706/http://www.ifa.hawaii.edu/~jewitt/irregulars.html David Jewitt pages]
* [https://web.archive.org/web/20150318034833/http://home.dtm.ciw.edu/users/sheppard/satellites/jupsatdata.html Jupiter's Known Satellites] (by [[Scott S. Sheppard]])
* [http://remanzacco.blogspot.co.uk/2012/11/two-irregular-satellites-of-jupiter.html Two Irregular Satellites of Jupiter] (Himalia & Elara: Remanzacco Observatory: November 23, 2012)

{{Moons of Jupiter}}
{{DEFAULTSORT:Himalia (Moon)}}
[[Category:Himalia group]]
[[Category:Moons of Jupiter]]
[[Category:Irregular satellites]]
[[Category:Astronomical objects discovered in 1904|19041203]]
[[Category:Discoveries by Charles D. Perrine]]
[[Category:Moons with a prograde orbit]]