121 Hermione

Template:Short description Template:Use dmy dates {{#invoke:infobox|infoboxTemplate | class = vcard | titleclass = fn org | title = 121 Hermione | image = {{#invoke:InfoboxImage|InfoboxImage|image=|upright={{#if:||1.1}}|alt=}} | caption = 121 Hermione and its moon | headerstyle = {{#if:#D6D6D6|background-color:#D6D6D6|background-color:#E0CCFF}}; color:inherit; | labelstyle = max-width:{{#if:||11em}}; | autoheaders = y

| header1 = Discovery<ref name="MPC-object" />

| label2 = Discovered by | data2 = James Craig Watson | label3 = Discovery site | data3 = | label4 = Discovery date | data4 = 12 May 1872 | label5 = Template:Longitem | data5 =

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

| label11 = Template:Longitem | data11 = (121) Hermione | label12 = Pronunciation | data12 = Template:IPAc-en<ref>Noah Webster (1884) A Practical Dictionary of the English Language</ref> | label13 = Template:Longitem | data13 = Hermione<ref name="springer" />
Template:Small | label14 = Template:Longitem | data14 = A872 JA; 1970 VE | label15 = Template:Longitem | data15 = main-beltTemplate:·Cybele | label16 = Adjectives | data16 = Hermionean Template:IPAc-en | label17 = Symbol | data17 =

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

| data21 = | data22 = {{#if:23 March 2018 (JD 2458200.5) |Epoch 23 March 2018 (JD 2458200.5)}} | data23 = {{#if:0 | Uncertainty parameter 0}} | label24 = Observation arc | data24 = 145.96 yr (53,312 d) | label25 = Earliest precovery date | data25 = | label26 = {{#switch:{{{apsis}}} |apsis|gee|barion|center|centre|(apsis)=Apo{{{apsis}}} |Ap{{#if:|{{{apsis}}}|helion}}}} | data26 = 3.9067 AU | label27 = Peri{{#if:|{{{apsis}}}|helion}} | data27 = 2.9889 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 = 3.4478 AU | label33 = Template:Longitem | data33 = | label34 = Eccentricity | data34 = 0.1331 | label35 = Template:Longitem | data35 = 6.40 yr (2,338 d) | label36 = Template:Longitem | data36 = | label37 = Template:Longitem | data37 = | label38 = Template:Longitem | data38 = 157.08° | label39 = Template:Longitem | data39 = Template:Deg2DMS / day | label40 = Inclination | data40 = 7.5975° | label41 = Template:Longitem | data41 = | label42 = Template:Longitem | data42 = 73.127° | label43 = Template:Longitem | data43 = | label44 = Template:Longitem | data44 = | label45 = Template:Longitem | data45 = 298.18° | label46 = Template:Nowrap | data46 = | label47 = Satellite of | data47 = | label48 = Group | data48 = | label49 = {{#switch: |yes|true=Satellites |Known satellites}} | data49 = S/2002 (121) 1 | 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}}} 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 = 268 × 186 × 183 km<ref name=Baer>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
(254 ± 4) × (125 ± 9) km<ref name=MarKaaHom06>Template:Cite journal</ref> | label72 = Template:Longitem | data72 = | label73 = Template:Longitem | data73 = 95 km<ref name=MarKaaHom06/> | 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=MarHesDes05/> | label80 = Mass | data80 = Template:Val<ref name=MarHesDes05>Template:Cite journal</ref> | label81 = Template:Longitem | data81 = 1.8 ± 0.2 g/cm³<ref name=MarHesDes05/>Template:Efn | label82 = Template:Longitem | data82 = 0.022 m/s²Template:Efn | label83 = Template:Longitem | data83 = | label84 = Template:Longitem | data84 = 0.075 km/sTemplate:Efn | label85 = Template:Longitem | data85 = | label86 = Template:Longitem | data86 = 0.2313 d (5.551 h)<ref name=IAUC8264>IAUC 8264 Template:Webarchive</ref> | label87 = Template:Longitem | data87 = | label88 = Template:Longitem | data88 = 73° | label89 = Template:Longitem | data89 = | label90 = Template:Longitem | data90 = | label91 = Template:Longitem | data91 = 1.5 ± 2° | label92 = Template:Longitem | data92 = +10 ± 2°<ref name=MarHesDes05/> | label93 = {{#if:yes |Template:Longitem |Albedo}} | data93 = 0.0482 ± 0.002<ref name=IRAS>Supplemental IRAS minor planet survey Template:Webarchive</ref> | 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 = C<ref name=PDStax>PDS node taxonomy database Template:Webarchive</ref> | label104 = Template:Longitem | data104 = | label105 = Template:Longitem | data105 = | label106 = Template:Longitem | data106 = 7.31<ref name=IRAS/> | label107 = Template:Longitem | data107 =

| header110 = Atmosphere

| label111 = Template:Longitem | data111 = | label112 = Template:Longitem | data112 = | label113 = Composition by volume | data113 =

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

}}{{#invoke:Check for unknown parameters|check|unknown=Template:Main other|preview=Page using Template:Infobox planet with unknown parameter "_VALUE_"|ignoreblank=y| abs_magnitude | adjective | adjectives | albedo | allsatellites | alt_names | angular_dist | angular_size | aphelion | apoapsis | apsis | apoastron | arg_peri | asc_node | atmosphere | atmosphere_composition | atmosphere_ref | avg_speed | axial_tilt | background | barycentric | bgcolour | caption | circumference | declination | density | dimensions | discovered | discoverer | discovery_method | discovery_ref | discovery_site | earliest_precovery_date | eccentricity | epoch | equatorial_radius | escape_velocity | exosolar planets | extrasolarplanet | family | flattening | group | image | image_alt | image_scale | inclination | jupiter_moid | label_width | long_periastron | magnitude | mars_moid | mass | max_temp_1 | max_temp_2 | max_temp_3 | max_temp_4 | mean_anomaly | mean_diameter | mean_motion | mean_orbit_radius | mean_radius | mean_temp_1 | mean_temp_2 | mean_temp_3 | mean_temp_4 | mercury_moid | min_temp_1 | min_temp_2 | min_temp_3 | min_temp_4 | minorplanet | moid | moment_of_inertia_factor | mp_category | mp_name | mpc_name | name | named_after | neptune_moid | node_rate | note | observation_arc | orbit_diagram | orbit_ref | p_eccentricity | p_inclination | p_mean_motion | p_orbit_ref | p_semimajor | periapsis | periastron | perihelion | perihelion_rate | period | physical_ref | polar_radius | pole_ecliptic_lat | pole_ecliptic_lon | pronounce | pronounced | right_asc_north_pole | rot_velocity | rotation | satellite_of | satellites | saturn_moid | scale_height | semi-amplitude | semimajor | sidereal_day | single_temperature | spectral_type | star | surface_area | surface_grav | surface_pressure | surface_absorbed_dose_rate | surface_equivalent_dose_rate | symbol | synodic_period | temp_name1 | temp_name2 | temp_name3 | temp_name4 | time_periastron | tisserand | uncertainty | uranus_moid | venus_moid | volume }}

121 Hermione is a very large binary asteroid discovered in 1872. It orbits in the Cybele group in the far outer asteroid belt.<ref name=tanton/> As an asteroid of the dark C spectral type, it is probably composed of carbonaceous materials. In 2002, a small moon was found to be orbiting Hermione.<ref name=tanton>Template:Cite book</ref>

Discovery

Hermione was discovered by J. C. Watson on 12 May 1872 from Ann Arbor, Michigan, in the United States,<ref name=tanton/> and named after Hermione, daughter of Menelaus and Helen in Greek mythology.<ref name="springer" />

Physical properties

File:121Hermione (Lightcurve Inversion).png

Lightcurve-based 3D-model of Hermione

File:121 hermione.png

Lightcurve-based 3D-model of Hermione on the top and an image of the asteroid on the bottom.

The asteroid has a bi-lobed shape, as evidenced by adaptive optics images, the first of which were taken in December 2003 with the Keck telescope.<ref name=MarKaaHom06/> Of several proposed shape models that agreed with the images, a "snowman"-like shape was found to best fit the observed precession rate of Hermione's satellite.<ref name="MarHesDes05" /> In this "snowman" model, the asteroid's shape can be approximated by two partially overlapping spheres of radii 80 and 60 km, whose centers are separated by a distance of 115 km. A simple ellipsoid shape was ruled out.

Observation of the satellite's orbit has made possible an accurate determination of Hermione's mass.<ref name=MarHesDes05/> For the best-fit "snowman" model, the density is found to be 1.8 ± 0.2 g/cm³, giving a porosity on the order of 20%, and possibly indicating that the main components are fractured solid bodies, rather than the asteroid being a rubble pile.

Occultations by Hermione have been successfully observed three times so far, the last time in February 2004. {{#invoke:infobox|infoboxTemplate | class = vcard | titleclass = fn org | title = S/2002 (121) 1 | image = {{#invoke:InfoboxImage|InfoboxImage|image=|upright={{#if:||1.1}}|alt=}} | caption = | headerstyle = {{#if:#A0FFA0|background-color:#A0FFA0|background-color:#E0CCFF}}; color:inherit; | labelstyle = max-width:{{#if:||11em}}; | autoheaders = y

| header1 = Discovery<ref name="iauc7980">IAUC 7980 Template:Webarchive</ref>

| label2 = Discovered by | data2 = W. J. Merline,
P. M. Tamblyn,
C. Dumas,
L. M. Close,
C. R. Chapman,
F. Menard,
W. M. Owen,
and D. C. Slater | label3 = Discovery site | data3 = | label4 = Discovery date | data4 = 2002-09-28 | label5 = Template:Longitem | data5 =

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

| label11 = Template:Longitem | data11 = | label12 = Pronunciation | data12 = | label13 = Template:Longitem | data13 = | label14 = Template:Longitem | data14 = LaFayette | label15 = Template:Longitem | data15 = main-beltTemplate:·Cybele | label16 = Adjectives | data16 = | label17 = Symbol | data17 =

| header20 = Orbital characteristics{{#ifeq:|yes| (barycentric)}}<ref name=marchis>121 Hermione and S/2002 (121) 1, orbit data website maintained by F. Marchis.</ref>

| data21 = | data22 = {{#if: |Epoch {{{epoch}}}}} | 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 = 768 ± 11 km | label33 = Template:Longitem | data33 = | label34 = Eccentricity | data34 = 0.001 ± 0.001 | label35 = Template:Longitem | data35 = 2.582 ± 0.002 d | label36 = Template:Longitem | data36 = | label37 = Template:Longitem | data37 = | label38 = Template:Longitem | data38 = | label39 = Template:Longitem | data39 = | label40 = Inclination | data40 = 3 ± 2°
Template:Small | 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 = 121 Hermione | label48 = Group | data48 = | 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}}} 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 = 12 ± 4 km<ref name=MarKaaHom06/> | label72 = Template:Longitem | data72 = | 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 = ~1.6Template:E kgTemplate:Efn | label81 = Template:Longitem | data81 = | label82 = Template:Longitem | data82 = | label83 = Template:Longitem | data83 = | label84 = Template:Longitem | data84 = | label85 = Template:Longitem | data85 = | 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:yes |Template:Longitem |Albedo}} | data93 = | 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 = | label104 = Template:Longitem | data104 = | label105 = Template:Longitem | data105 = | label106 = Template:Longitem | data106 = 13.0<ref name=MarKaaHom06/> | label107 = Template:Longitem | data107 =

| header110 = Atmosphere

| label111 = Template:Longitem | data111 = | label112 = Template:Longitem | data112 = | label113 = Composition by volume | data113 =

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

}}{{#invoke:Check for unknown parameters|check|unknown=Template:Main other|preview=Page using Template:Infobox planet with unknown parameter "_VALUE_"|ignoreblank=y| abs_magnitude | adjective | adjectives | albedo | allsatellites | alt_names | angular_dist | angular_size | aphelion | apoapsis | apsis | apoastron | arg_peri | asc_node | atmosphere | atmosphere_composition | atmosphere_ref | avg_speed | axial_tilt | background | barycentric | bgcolour | caption | circumference | declination | density | dimensions | discovered | discoverer | discovery_method | discovery_ref | discovery_site | earliest_precovery_date | eccentricity | epoch | equatorial_radius | escape_velocity | exosolar planets | extrasolarplanet | family | flattening | group | image | image_alt | image_scale | inclination | jupiter_moid | label_width | long_periastron | magnitude | mars_moid | mass | max_temp_1 | max_temp_2 | max_temp_3 | max_temp_4 | mean_anomaly | mean_diameter | mean_motion | mean_orbit_radius | mean_radius | mean_temp_1 | mean_temp_2 | mean_temp_3 | mean_temp_4 | mercury_moid | min_temp_1 | min_temp_2 | min_temp_3 | min_temp_4 | minorplanet | moid | moment_of_inertia_factor | mp_category | mp_name | mpc_name | name | named_after | neptune_moid | node_rate | note | observation_arc | orbit_diagram | orbit_ref | p_eccentricity | p_inclination | p_mean_motion | p_orbit_ref | p_semimajor | periapsis | periastron | perihelion | perihelion_rate | period | physical_ref | polar_radius | pole_ecliptic_lat | pole_ecliptic_lon | pronounce | pronounced | right_asc_north_pole | rot_velocity | rotation | satellite_of | satellites | saturn_moid | scale_height | semi-amplitude | semimajor | sidereal_day | single_temperature | spectral_type | star | surface_area | surface_grav | surface_pressure | surface_absorbed_dose_rate | surface_equivalent_dose_rate | symbol | synodic_period | temp_name1 | temp_name2 | temp_name3 | temp_name4 | time_periastron | tisserand | uncertainty | uranus_moid | venus_moid | volume }}

Moon

A satellite of Hermione was discovered in 2002 with the Keck II telescope.<ref name=tanton/> It is about 8 miles (13 km) in diameter.<ref name=tanton/> The satellite is provisionally designated S/2002 (121) 1. It has not yet been officially named, but "LaFayette" has been proposed by a group of astronomers in reference to the frigate used in secret by the Marquis de Lafayette to reach America to help the insurgents.<ref name="Johnston"/><ref name=MarKaaHom06/>

External links

• 121 Hermione and S/2002 (121) 1, orbit data website maintained by F. Marchis. Includes adaptive optics images, orbit diagrams, and shape models.
• (121) Hermione, datasheet, johnstonsarchive.net
• Asteroids with Satellites, Robert Johnston, johnstonsarchive.net
• Tally of Asteroids Harboring Moons Grows Beyond 30 (Space.com, 3 October 2002)
• Template:AstDys
• Template:JPL small body

Template:Minor planets navigator {{#invoke:Navbox|navbox}} Template:Authority control