18 Melpomene
Template:Short description Template:Use dmy dates {{#invoke:infobox|infoboxTemplate | class = vcard | titleclass = fn org | title = 18 Melpomene | image = {{#invoke:InfoboxImage|InfoboxImage|image=18 Melpomene VLT (2021), deconvolved.pdf|upright={{#if:||1.1}}|alt=}} | caption = | headerstyle = {{#if:#D6D6D6|background-color:#D6D6D6|background-color:#E0CCFF}} | labelstyle = max-width:{{#if:||11em}}; | autoheaders = y
| header1 = Discovery
| label2 = Discovered by | data2 = John Russell Hind | label3 = Discovery site | data3 = | label4 = Discovery date | data4 = 24 June 1852 | label5 = Template:Longitem | data5 =
| header10 = {{#if:|Designations|Designations}}
| label11 = Template:Longitem | data11 = (18) Melpomene | label12 = Pronunciation | data12 = Template:IPAc-en<ref>Noah Webster (1884) A Practical Dictionary of the English Language</ref> | label13 = Template:Longitem | data13 = Melpomenē | label14 = Template:Longitem | data14 = | label15 = Template:Longitem | data15 = Main belt | label16 = Adjectives | data16 = Melpomenean Template:IPAc-en<ref>Tim Shephard (2014) Echoing Helicon</ref> | label17 = Symbol | data17 = File:Melpomene symbol (bold).svg (historical)
| header20 = Orbital characteristics{{#ifeq:|yes| (barycentric)}}<ref name=jpldata/>
| 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 = Template:Convert
| label27 = Peri{{#if:|{{{apsis}}}|helion}}
| data27 = Template:Convert
| 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:Convert
| label33 = Template:Longitem
| data33 =
| label34 = Eccentricity
| data34 = 0.21827
| label35 = Template:Longitem
| data35 = Template:Cvt
| label36 = Template:Longitem
| data36 =
| label37 = Template:Longitem
| data37 =
| label38 = Template:Longitem
| data38 = 113.8711°
| label39 = Template:Longitem
| data39 =
| label40 = Inclination
| data40 = 10.132°
| label41 = Template:Longitem
| data41 =
| label42 = Template:Longitem
| data42 = 150.34°
| label43 = Template:Longitem
| data43 =
| label44 = Template:Longitem
| data44 = 2023-Sep-11
| label45 = Template:Longitem
| data45 = 228.05°
| 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 = Template:Convert
| label52 = Mercury MOID
| data52 =
| label53 = Venus MOID
| data53 =
| label54 = Mars MOID
| data54 =
| label55 = Jupiter MOID
| data55 = Template:Convert
| label56 = Saturn MOID
| data56 =
| label57 = Uranus MOID
| data57 =
| label58 = Neptune MOID
| data58 =
| label59 = TJupiter
| data59 = 3.543
| 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}}} degTemplate:\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}}} arcsecTemplate:\yr }}
| label67 = Template:Longitem
| data67 = {{#if:|{{{node_rate}}} arcsecTemplate:\yr}}
| header70 = Template:Anchor{{#if:yes| Physical characteristics|Physical characteristics}}
| label71 = Dimensions
| data71 = Template:Nowrap<ref name=Baer/>
(150 × 125 km)<ref name=Hubble1999/>
(150 × 170 km)<ref name=Hubble2005/>
| label72 = Template:Longitem
| data72 = Template:Val<ref name=VLT>Template:Cite journal</ref>
Template:Val<ref name=jpldata/>
| label73 = Template:Longitem
| data73 =
| label74 = Template:Longitem
| data74 =
| label75 = Template:Longitem
| data75 =
| label76 = Flattening
| data76 = 0.19Template:Efn
| label77 = Circumference
| data77 =
| label78 = Template:Longitem
| data78 =
| label79 = Volume
| data79 =
| label80 = Mass
| data80 = Template:Val<ref name=VLT/>
3.0Template:E kg<ref name=Baer/>
| label81 = Template:Longitem
| data81 = Template:Val<ref name=VLT/>
Template:Val<ref name=Baer/>
| label82 = Template:Longitem
| data82 =
| label83 = Template:Longitem
| data83 =
| label84 = Template:Longitem
| data84 =
| label85 = Template:Longitem
| data85 = Template:Cvt<ref name=jpldata/>
Template:Val<ref name=VLT/>
Template:Cvt<ref name=AstroSurf/>
| label86 = Template:Longitem
| data86 =
| label87 = Template:Longitem
| data87 =
| label88 = Template:Longitem
| data88 = 64°<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 = 0.221 (calculated)<ref name=VLT/>
0.223<ref name=ADA/>
0.181 ± 0.033<ref name=jpldata/>
| label94 = Temperature
| data94 =
| data100 = {{#if:|
{{#if:|}}{{#if:|}}{{#if:|}}{{#if:|}}Surface temp. | min | mean | max |
---|---|---|---|
{{{temp_name1}}} | |||
{{{temp_name2}}} | |||
{{{temp_name3}}} | |||
{{{temp_name4}}} |
}}
| label101 = Surface absorbed dose rate
| data101 =
| label102 = Surface equivalent dose rate
| data102 =
| label103 = Template:Longitem
| data103 = S<ref name=jpldata/><ref name=VLT/>
| label104 = Template:Longitem
| data104 =
| label105 = Template:Longitem
| data105 = 7.5<ref name="Pasachoff1983"/> to 12.0
| label106 = Template:Longitem
| data106 = 6.35<ref name=jpldata/>
6.51<ref name=VLT/>
| label107 = Template:Longitem
| data107 = 0.23" to 0.059"
| header110 = Atmosphere
| label111 = Template:Longitem | data111 = | label112 = Template:Longitem | data112 = | label113 = Composition by volume | data113 =
| below = {{#if:||Template:Reflist }}
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18 Melpomene is a large, bright main-belt asteroid that was discovered by J. R. Hind on 24 June 1852,<ref name="IAU_MPC"/> and named after Melpomenē, the Muse of tragedy in Greek mythology. Its historical symbol was a dagger over a star; as of 2023 it was in the pipeline for Unicode 17.0 as U+1CECB (File:Melpomene symbol (fixed width).svg).<ref name=astunicode>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name=pipeline>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Melpomene is classified as an S-type asteroid and is composed of silicates and metals. This asteroid is orbiting the Sun at a distance of Template:Cvt with a period of Template:Convert and an eccentricity (ovalness) of 0.22. The orbital plane is tilted at an angle of 10.1° to the plane of the ecliptic.<ref name=jpldata/>
Melpomene occulted the star SAO 114159 on 11 December 1978. A possible Melpomenean satellite with a diameter of at least 37 km was detected. The satellite candidate received a provisional designation S/1978 (18) 1.<ref name=IAUC3315/> In 1988 a search for satellites or dust orbiting this asteroid was performed using the UH88 telescope at the Mauna Kea Observatories, but the effort came up empty.<ref name="Gradie1988"/> Melpomene was observed with the Hubble Space Telescope in 1993. It was able to resolve the asteroid's slightly elongated shape, but no satellites were detected.<ref name=Hubble1999/>
Melpomene has been studied by radar.<ref name="detected"/> Photometric observations during 2012 provided a rotation period of Template:Val with a brightness variation of Template:Val in magnitude, which is consistent with previous studies.<ref name=Pilcher2013/> It has a mean diameter of Template:Val.<ref name=VLT/><ref name=jpldata/>
Melpomene can reach an apparent magnitude of +7.9 at a favorable opposition near perihelion, such as occurred in September 2002 when it was Template:Convert from Earth.<ref name="Horizons2002"/>
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