Himalia (moon)

Template:Short description Template:Use dmy dates Template:About {{#invoke:infobox|infoboxTemplate | class = vcard | titleclass = fn org | title = Himalia | image = {{#invoke:InfoboxImage|InfoboxImage|image=Himalia.png|upright={{#if:||1.1}}|alt=}} | caption = Low-resolution image of Himalia from Cassini, December 2000 | headerstyle = {{#if:|background-color:|background-color:#E0CCFF}} | labelstyle = max-width:{{#if:||11em}}; | autoheaders = y

| header1 = Discovery<ref name="Discovery"/>

| header10 = {{#if:|Designations|Designations}}

| header20 = Orbital characteristics{{#ifeq:|yes| (barycentric)}}<ref name="MPC115889"/>

| data21 = | data22 = {{#if:27 April 2019 (JD 2458600.5) |Epoch 27 April 2019 (JD 2458600.5)}} | data23 = {{#if: | Uncertainty parameter {{{uncertainty}}}}} | label24 = Observation arc | data24 = 114.25 yr (41,728 days) | label25 = Earliest precovery date | data25 = | label26 = {{#switch:{{{apsis}}} |apsis|gee|barion|center|centre|(apsis)=Apo{{{apsis}}} |Ap{{#if:|{{{apsis}}}|helion}}}} | data26 = | label27 = Peri{{#if:|{{{apsis}}}|helion}} | data27 = | label28 = Peri{{#if:|{{{apsis}}}|apsis}} | data28 = | label29 = {{#switch:{{{apsis}}} |helion|astron=Ap{{{apsis}}} |Apo{{#if:|{{{apsis}}}|apsis}}}} | data29 = | label30 = Periastron | data30 = | label31 = Apoastron | data31 = | label32 = Template:Longitem | data32 = Template:Cvt | label33 = Template:Longitem | data33 = | label34 = Eccentricity | data34 = 0.1537860 | label35 = Template:Longitem | data35 = +248.29 d | label36 = Template:Longitem | data36 = | label37 = Template:Longitem | data37 = | label38 = Template:Longitem | data38 = 94.30785° | label39 = Template:Longitem | data39 = Template:Deg2DMS / day | label40 = Inclination | data40 = 29.90917° Template:Small | label41 = Template:Longitem | data41 = | label42 = Template:Longitem | data42 = 44.99935° | label43 = Template:Longitem | data43 = | label44 = Template:Longitem | data44 = | label45 = Template:Longitem | data45 = 21.60643° | label46 = Template:Nowrap | data46 = | label47 = Satellite of | data47 = Jupiter | label48 = Group | data48 = Himalia group | label49 = {{#switch: |yes|true=Satellites |Known satellites}} | data49 = | label50 = Star | data50 = | label51 = Earth MOID | data51 = | label52 = Mercury MOID | data52 = | label53 = Venus MOID | data53 = | label54 = Mars MOID | data54 = | label55 = Jupiter MOID | data55 = | label56 = Saturn MOID | data56 = | label57 = Uranus MOID | data57 = | label58 = Neptune MOID | data58 = | label59 = T_Jupiter | data59 =

| header60 = Proper orbital elements

| label61 = Template:Longitem | data61 = {{#if: |{{{p_semimajor}}} AU}} | label62 = Template:Longitem | data62 = | label63 = Template:Longitem | data63 = | label64 = Template:Longitem | data64 = {{#if: |{{{p_mean_motion}}} deg Template:\yr}} | label65 = Template:Longitem | data65 = {{#if:|{{#expr:360/1 round 5}} yr
({{#expr:365.25*360/1 round 3}} d) }} | label66 = Template:Longitem | data66 = {{#if:|{{{perihelion_rate}}} arcsec Template:\yr }} | label67 = Template:Longitem | data67 = {{#if:|{{{node_rate}}} arcsec Template:\yr}}

| header70 = Template:Anchor{{#if:| Physical characteristics|Physical characteristics}}

| label71 = Dimensions | data71 = 205.6 × 141.3 km Template:Small<ref name="occultation"/>
Template:Val × Template:Val km (Cassini estimate)<ref name="Porco2003"/> | label72 = Template:Longitem | data72 = Template:Val<ref name="Grav2015"/> | label73 = Template:Longitem | data73 = | label74 = Template:Longitem | data74 = | label75 = Template:Longitem | data75 = | label76 = Flattening | data76 = | label77 = Circumference | data77 = | label78 = Template:Longitem | data78 = | label79 = Volume | data79 = | label80 = Mass | data80 = Template:Val<ref name="Emelyanov2005" /> | label81 = Template:Longitem | data81 = Template:Val (assuming radius 85 km)<ref name="Emelyanov2005" />Template:Efn | label82 = Template:Longitem | data82 = ~ 0.062 m/s² (0.006 g) | label83 = Template:Longitem | data83 = | label84 = Template:Longitem | data84 = ~ 0.100 km/s | label85 = Template:Longitem | data85 = Template:Val<ref name="Pilcher2012"/> | label86 = Template:Longitem | data86 = | label87 = Template:Longitem | data87 = | label88 = Template:Longitem | data88 = | label89 = Template:Longitem | data89 = | label90 = Template:Longitem | data90 = | label91 = Template:Longitem | data91 = | label92 = Template:Longitem | data92 = | label93 = {{#if: |Template:Longitem |Albedo}} | data93 = Template:Val<ref name="Grav2015"/> | label94 = Temperature | data94 =

| data100 = {{#if:|

Surface temp.	min	mean	max
{{{temp_name1}}}
{{{temp_name2}}}
{{{temp_name3}}}
{{{temp_name4}}}

}}

| header110 = Atmosphere

| below = {{#if:||Template:Reflist }}

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Himalia (Template:IPAc-en), also known as Jupiter VI, is the largest irregular satellite of Jupiter. With a diameter of at least Template:Convert,<ref name="occultation"/> it is the sixth largest Jovian satellite, after the four Galilean moons and Amalthea. It was discovered by Charles Dillon Perrine at the Lick Observatory on 3 December 1904 and is named after the nymph 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.Template:Efn

DiscoveryEdit

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"> Template:Cite journal;
Template:Cite journal;
Template:Cite journal;
Template:Cite journal </ref> Himalia is Jupiter's most easily observed small satellite; though Amalthea is brighter, its proximity to the planet's brilliant disk makes it a far more difficult object to view.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

NameEdit

Himalia is named after the nymph 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">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> before then, it was simply known as Template:Nowrap or Jupiter Satellite VI, although calls for a full name appeared shortly after its and Elara's discovery; A.C.D. Crommelin wrote in 1905: Template:Cquote

The moon was sometimes called Hestia, after the Greek goddess, from 1955 to 1975.<ref name="Gaposchkin">Template:Cite book</ref>

OrbitsEdit

[[File:Animation of Himalia orbit around Jupiter.gif|thumb|upright|left|Animation of Himalia's orbit.
Template:Legend2 Template:·Template:Legend2 Template:·Template:Legend2•{{ Template:Legend2

At a distance of about Template:Convert from Jupiter, Himalia takes about 250 Earth days to complete one orbit around Jupiter.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> It is the largest member of the Himalia group, which are a group of small moons orbiting Jupiter at a distance from Template:Convert to Template:Convert, with inclined orbits at an angle of 27.5 degrees to Jupiter's equator.<ref name=Jewitt2004>Template:Cite book</ref> Their orbits are continuously changing due to solar and planetary perturbations.<ref name="Jacobson2000">Template:Cite journal</ref>

Physical characteristicsEdit

[[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

Himalia observed by the Wide-field Infrared Survey Explorer (WISE) spacecraft in 2014

Himalia's rotational period is Template:Val Template:Val Template:Val.<ref name="Pilcher2012" /> Himalia appears neutral in color (grey), like the other members of its group, with 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 spectrum, with a slight absorption at Template:Val, which could indicate the presence of water.<ref name="Chamberlain">Template:Cite journal</ref> Although Himalia is the sixth-largest moon of Jupiter, it is the fifth-most massive. Amalthea is only a few km bigger, but less massive. Resolved images of Himalia by Cassini have led to a size estimate of Template:Convert, while ground-based estimates suggest that Himalia is large, with a diameter around Template:Convert.<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 US state of Georgia.<ref name="occultation"/> From the occultation, Himalia was given a size estimate of Template:Convert, in agreement with earlier ground-based estimates.<ref name="occultation"/>

MassEdit

In 2005, Emelyanov estimated Himalia to have a mass of Template:Val (GM=0.28±0.04), based on a perturbation of Elara on July 15, 1949 (when the distance between them became a mere 64246.04 kilometers).<ref name="Emelyanov2005">Template:Cite journal</ref> JPL's Solar System dynamics website assumes that Himalia has a mass of Template:Val (GM=0.15) with a radius of Template:Val.<ref name="jplssd" />

Himalia's density will depend on whether it has an average radius of about Template:Val (geometric mean from Cassini)<ref name=Emelyanov2005/> or a radius closer to Template:Val.<ref name="jplssd" />

File:Cassini-Huygens Image of Himalia.png

Cassini image of Himalia, taken in December 2000 from a distance of 4.4 million kilometres

Source	Radius km	Density g/cm³	Mass kg
Emelyanov	67	3.33	4.2Template:E
Emelyanov	85	1.63Template:Efn	4.2Template:E
JPL SSD	85	0.88	2.3Template:E

ExplorationEdit

File:Himalia - New Horizons.png

Phases of Himalia imaged by the LORRI instrument aboard New Horizons

In November 2000, the Cassini spacecraft, en route to Saturn, made a number of images of Himalia, including photos from a distance of 4.4 million km. Himalia covers only a few pixels, but seems to be an elongated object with axes Template:Val and Template:Val, 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 million km. Again, Himalia appears only a few pixels across.<ref name="PlanetarySoc" />

Himalia ringEdit

File:Himalia ring.jpg

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 planetary ring parallel with and slightly inside Himalia's orbit. Because the small (4-km) 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">{{#invoke:citation/CS1|citation |CitationClass=web }}</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">Template:Cite conference</ref> The recovery of Dia in 2010 and 2011 disproved any connection between Dia and the Himalia ring.<ref name="MPEC2012-R22">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref> {{#invoke:citation/CS1|citation |CitationClass=web }} </ref>