Galatea (moon)

Template:Short description Template:For {{#invoke:infobox|infoboxTemplate | class = vcard | titleclass = fn org | title = Galatea | image = {{#invoke:InfoboxImage|InfoboxImage|image=Galatea moon.jpg|upright={{#if:||1.1}}|alt=}} | caption = Galatea as seen by Voyager 2 (elongation is due to smearing) | headerstyle = {{#if:|background-color:|background-color:#E0CCFF}} | labelstyle = max-width:{{#if:||11em}}; | autoheaders = y

| header1 = Discovery

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

| header20 = Orbital characteristics{{#ifeq:|yes| (barycentric)}}<ref name="Jacobson2004" /><ref name="Showalter2019" />

| data21 = | data22 = {{#if:18 August 1989 |Epoch 18 August 1989}} | data23 = {{#if: | Uncertainty parameter {{{uncertainty}}}}} | label24 = Observation arc | data24 = | 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:Val | label33 = Template:Longitem | data33 = | label34 = Eccentricity | data34 = 0.00022 ± 0.00008 | label35 = Template:Longitem | data35 = 0.42874431 ± 0.00000001 d | label36 = Template:Longitem | data36 = | label37 = Template:Longitem | data37 = | label38 = Template:Longitem | data38 = | label39 = Template:Longitem | data39 = | label40 = Inclination | data40 = Template:Ubl | label41 = Template:Longitem | data41 = | label42 = Template:Longitem | data42 = | label43 = Template:Longitem | data43 = | label44 = Template:Longitem | data44 = | label45 = Template:Longitem | data45 = | label46 = Template:Nowrap | data46 = | label47 = Satellite of | data47 = Neptune | label48 = Group | data48 = ring shepherd | 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 = (Template:Val) × (Template:Val) × (Template:Val) km<ref name="Karkoschka2003" /> | label72 = Template:Longitem | data72 = | label73 = Template:Longitem | data73 = Template:Val<ref name="Karkoschka2003" /> | label74 = Template:Longitem | data74 = | label75 = Template:Longitem | data75 = | label76 = Flattening | data76 = | label77 = Circumference | data77 = | label78 = Template:Longitem | data78 = | label79 = Volume | data79 = ~Template:Val<ref name="Volume" group="lower-alpha" /> | label80 = Mass | data80 = Template:Val<ref>Giuliatti Winter et al. (2020), as cited in Madeira & Giuliatti Winter (2022).<ref name="Madeira & GiuliattiWinter 2022"/></ref> | label81 = Template:Longitem | data81 = ~Template:Val<ref name="Density" group="lower-alpha" /> | label82 = Template:Longitem | data82 = ~Template:Gr–Template:Gr m/s²<ref name="Surface gravity" group="lower-alpha" /> | label83 = Template:Longitem | data83 = | label84 = Template:Longitem | data84 = ~Template:V2–Template:V2 km/s<ref name="Escape velocity" group="lower-alpha" /> | label85 = Template:Longitem | data85 = synchronous | label86 = Template:Longitem | data86 = | label87 = Template:Longitem | data87 = | label88 = Template:Longitem | data88 = zero | label89 = Template:Longitem | data89 = | label90 = Template:Longitem | data90 = | label91 = Template:Longitem | data91 = | label92 = Template:Longitem | data92 = | label93 = {{#if: |Template:Longitem |Albedo}} | data93 = 0.08<ref name="Karkoschka2003" /><ref name="jplssd" /> | label94 = Temperature | data94 = ~51 K mean (estimate)

| 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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Galatea Template:IPAc-en, also known as Neptune VI, is the fourth-closest inner moon of Neptune, and fifth-largest moon of Neptune. It is named after Galatea, one of the fifty Nereids of Greek legend, with whom Cyclops Polyphemus was vainly in love.

DiscoveryEdit

File:Galatea feat.jpg

Galatea inside of a faint ring arc near Neptune

Galatea was discovered in late July 1989 from the images taken by the Voyager 2 probe. It was given the temporary designation S/1989 N 4.<ref name="IAUC 4824" /> The discovery was announced (IAUC 4824) on 2 August 1989, and mentions "10 frames taken over 5 days", implying a discovery date of sometime before July 28. The name was given on 16 September 1991.<ref name="IAUC 5347" />

Physical propertiesEdit

Galatea is irregularly shaped and shows no sign of any geological modification. It is likely that it is a rubble pile re-accreted from fragments of Neptune's original satellites, which were smashed up by perturbations from Triton soon after that moon's capture into a very eccentric initial orbit.<ref name="BanfieldMurray1992" />

Compositionally, Galatea appears to be similar to other small inner Neptunian satellites, with a deep 3.0 micron feature attributed to water ice or hydrated silicate minerals. It has a 0.08 albedo at 1.4 and 2.0 microns, dropping to 0.04 at 3.0 microns, and increasing to 0.12 at 4.6 microns.<ref>Template:Cite journal</ref>

OrbitEdit

Galatea's orbit lies below Neptune's synchronous orbit radius, so it is slowly spiralling inward due to tidal deceleration and may eventually impact the planet or break up into a new planetary ring system upon passing its Roche limit due to tidal stretching.

Galatea appears to be a shepherd moon for the Adams ring that is Template:Convert outside its orbit. Resonances with Galatea in the ratio 42:43 are also considered the most likely mechanism for confining the unique ring arcs that exist in this ring.<ref name="NamouniPorco" /> Galatea's mass has been estimated based on the radial perturbations it induces on the ring.<ref name="Porco1991" /><ref name="Madeira & GiuliattiWinter 2022"/>

NotesEdit

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Since Galatea is irregularly shaped, the actual surface gravity and escape velocity will vary significantly between different positions on the surface.

ReferencesEdit

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External linksEdit

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{{#invoke:Navbox|navbox}} Template:Solar System moons (compact) Template:Neptune