24 Themis

Template:Short description Template:For Template:Use dmy dates {{#invoke:infobox|infoboxTemplate | class = vcard | titleclass = fn org | title = 24 Themis | image = {{#invoke:InfoboxImage|InfoboxImage|image=24 Themis VLT (2021), deconvolved.pdf|upright={{#if:||1.1}}|alt=}} | caption = Deconvolved image of Themis by VLT-SPHERE | headerstyle = {{#if:#D6D6D6|background-color:#D6D6D6|background-color:#E0CCFF}} | labelstyle = max-width:{{#if:||11em}}; | autoheaders = y

| header1 = Discovery

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

| header20 = Orbital characteristics{{#ifeq:|yes| (barycentric)}}<ref name="jpldata">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

| data21 = | data22 = {{#if:17.0 October 2024 (JD 2460600.5) |Epoch 17.0 October 2024 (JD 2460600.5)}} | 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 = 524.4 Gm
(3.505 AU) | label27 = Peri{{#if:|{{{apsis}}}|helion}} | data27 = 415.9 Gm
(2.780 AU) | 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 = 470.2 Gm
(3.143 AU) | label33 = Template:Longitem | data33 = | label34 = Eccentricity | data34 = 0.1153 | label35 = Template:Longitem | data35 = 2035 d (5.57 yr) | label36 = Template:Longitem | data36 = | label37 = Template:Longitem | data37 = | label38 = Template:Longitem | data38 = 346.1° | label39 = Template:Longitem | data39 = | label40 = Inclination | data40 = 0.7368° | label41 = Template:Longitem | data41 = | label42 = Template:Longitem | data42 = 36.39° | label43 = Template:Longitem | data43 = | label44 = Template:Longitem | data44 = | label45 = Template:Longitem | data45 = 109.0° | label46 = Template:Nowrap | data46 = | label47 = Satellite of | data47 = | label48 = Group | data48 = | label49 = {{#switch: |yes|true=Satellites |Known satellites}} | data49 = | label50 = Star | data50 = | label51 = Earth MOID | data51 = 1.79422 AU | label52 = Mercury MOID | data52 = | label53 = Venus MOID | data53 = | label54 = Mars MOID | data54 = | label55 = Jupiter MOID | data55 = 1.50402 AU | label56 = Saturn MOID | data56 = | label57 = Uranus MOID | data57 = | label58 = Neptune MOID | data58 = | label59 = T_Jupiter | data59 = 3.199

| 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:yes| Physical characteristics|Physical characteristics}}

| label71 = Dimensions | data71 = Template:Nwr | label72 = Template:Longitem | data72 = Template:Val<ref name=VLT>P. Vernazza et al. (2021) VLT/SPHERE imaging survey of the largest main-belt asteroids: Final results and synthesis. Astronomy & Astrophysics 54, A56</ref>
Template:Val<ref name="astrometric">Template:Cite journal</ref> | label73 = Template:Longitem | data73 = | label74 = Template:Longitem | data74 = | label75 = Template:Longitem | data75 = | label76 = Flattening | data76 = 0.24Template:Efn | label77 = Circumference | data77 = | label78 = Template:Longitem | data78 = | label79 = Volume | data79 = | label80 = Mass | data80 = Template:Val<ref name=VLT/>
Template:Val<ref name="astrometric" />
Template:Val<ref name=Michalak2001>Template:Cite journal</ref>Template:Efn | label81 = Template:Longitem | data81 = Template:Val<ref name=VLT/>
Template:Val<ref name="astrometric" /> | label82 = Template:Longitem | data82 = Template:Val<ref name="astrometric" /> | label83 = Template:Longitem | data83 = | label84 = Template:Longitem | data84 = Template:Val<ref name="astrometric" /> | label85 = Template:Longitem | data85 = Template:Val Template:Nowrap<ref name="jpldata"/>
Template:Val<ref name=VLT/> | label86 = Template:Longitem | data86 = | label87 = Template:Longitem | data87 = | label88 = Template:Longitem | data88 = 18°<ref name=VLT/> | label89 = Template:Longitem | data89 = | label90 = Template:Longitem | data90 = | label91 = Template:Longitem | data91 = Template:Val<ref name=VLT/> | label92 = Template:Longitem | data92 = Template:Val<ref name=VLT/> | label93 = {{#if:yes |Template:Longitem |Albedo}} | data93 = 0.060 (calculated)<ref name=VLT/>
0.067<ref name="jpldata"/> | 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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24 Themis is one of the largest asteroids in the asteroid belt. At roughly Template:Convert in diameter, it is also the largest member of the Themistian family. It was discovered by Annibale de Gasparis on 5 April 1853. It is named after Themis, the personification of natural law and divine order in Greek mythology.

Discovery and observationsEdit

24 Themis was discovered on 5 April 1853 by Annibale de Gasparis of Naples, though it was given its name by fellow Italian astronomer Angelo Secchi. The asteroid was named after Themis, the Greek goddess of law.<ref>Template:Cite book</ref> Gravitational perturbations in the orbit of Themis were used to calculate the mass of Jupiter as early as 1875.<ref>Template:Cite journal</ref>

On 24 December 1975, 24 Themis had a close encounter with 2296 Kugultinov with a minimum distance of Template:Convert. By analyzing the perturbation of Kugultinov's orbit due to the gravitational pull of Themis, the mass of Themis was determined to be approximately Template:Val solar masses (Template:Val Earth masses).<ref name="CloseEncounters">Template:Cite conference</ref>

Orbit and rotationEdit

Themis is in an elliptical orbit around the Sun with an eccentricity of 0.1306 and an inclination of 0.76°.<ref name="AstroAlmanac">Template:Cite book</ref> It has an orbital period of 5.54 years. The distance between Themis and the Sun ranges from 2.71 AU at perihelion and 3.55 AU at aphelion,<ref name="Oxford dictionary"/> with a mean distance of 3.1302 AU.<ref name="AstroAlmanac"/> Themis is part of the Themis family of asteroids, which is located in the outer part of the main belt. The family consists of a core of large objects surrounded by a cloud of smaller objects; 24 Themis is a member of the core.<ref name="Oxford dictionary">Template:Cite encyclopedia</ref>

Surface materialsEdit

IceEdit

On 7 October 2009, the presence of water ice was confirmed on the surface of this asteroid using NASA’s Infrared Telescope Facility.<ref>Template:Cite magazine</ref><ref name="Atkinson2009">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The surface of the asteroid appears completely covered in ice. As this ice layer is sublimated, it may be getting replenished by a reservoir of ice under the surface.<ref name="ReferenceA">Template:Cite journal</ref><ref name= "Rivkin2010" />

Scientists hypothesize that some of the first water brought to Earth was delivered by asteroid impacts after the collision that produced the Moon. The presence of ice on 24 Themis supports this theory.<ref name="ReferenceA"/> Because of its proximity to the Sun, the widespread presence of ice on the surface of 24 Themis is somewhat unexpected. The surface ice may be replenished by a subsurface reservoir of ice or impact gardening—a phenomenon in which impact events overturn surface material at a rate of 1 m/ Gyr (billion years).<ref name="ReferenceA"/>

An alternative mechanism to explain the presence of water ice on 24 Themis is similar to the hypothesized formation of water on the surface of the Moon by solar wind. Trace amounts of water would be continuously produced by high-energy solar protons impinging oxide minerals present at the surface of the asteroid. The hydroxyl surface groups (S–OH) formed by the collision of protons (Template:Chem) with oxygen atoms present at oxide surface (S=O) can further be converted in water molecules (Template:Chem) adsorbed onto the oxide minerals surface. The chemical rearrangement supposed at the oxide surface could be schematically written as follows:

2 S-OH → S=O + S + Template:Chem

or,

2 S-OH → S–O–S + Template:Chem

where S represents the oxide surface.<ref name="Atkinson2009" />

OrganicsEdit

Organic compounds were also detected on the surface of Themis<ref name="ReferenceA"/><ref name= "Rivkin2010">Template:Cite journal (pdf version Template:Webarchive accessed 28 Feb. 2018).</ref> in the form of tholins, high-molecular weight organics found in the outer solar system, distinguished by a brown or reddish color in optical spectra. Compounds found in the spectra of Themis include ice tholin (the residual of an irradiated mixture of water ice and ethane), asphaltite, carbonaceous meteorite material, and polycyclic aromatic hydrocarbons.<ref name= "Rivkin2010"/><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>