624 Hektor

Template:Short description Template:Use dmy dates {{#invoke:infobox|infoboxTemplate | class = vcard | titleclass = fn org | title = 624 Hektor | image = {{#invoke:InfoboxImage|InfoboxImage|image=Hektor & Skamandrios 2006 Jul 16.PNG|upright={{#if:||1.1}}|alt=}} | caption = 624 Hektor and its moon Skamandrios | headerstyle = {{#if:#C2FFFF|background-color:#C2FFFF|background-color:#E0CCFF}} | labelstyle = max-width:{{#if:||11em}}; | autoheaders = y

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

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

| 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 = 111.28 yr (40,646 d) | label25 = Earliest precovery date | data25 = | label26 = {{#switch:{{{apsis}}} |apsis|gee|barion|center|centre|(apsis)=Apo{{{apsis}}} |Ap{{#if:|{{{apsis}}}|helion}}}} | data26 = 5.3824 AU | label27 = Peri{{#if:|{{{apsis}}}|helion}} | data27 = 5.1319 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 = 5.2571 AU | label33 = Template:Longitem | data33 = | label34 = Eccentricity | data34 = 0.0238 | label35 = Template:Longitem | data35 = 12.05 yr (4,403 d) | label36 = Template:Longitem | data36 = | label37 = Template:Longitem | data37 = | label38 = Template:Longitem | data38 = 136.09° | label39 = Template:Longitem | data39 = Template:Deg2DMS / day | label40 = Inclination | data40 = 18.166° | label41 = Template:Longitem | data41 = | label42 = Template:Longitem | data42 = 342.79° | label43 = Template:Longitem | data43 = | label44 = Template:Longitem | data44 = | label45 = Template:Longitem | data45 = 185.22° | label46 = Template:Nowrap | data46 = | label47 = Satellite of | data47 = | label48 = Group | data48 = | label49 = {{#switch: |yes|true=Satellites |Known satellites}} | data49 = 1 | label50 = Star | data50 = | label51 = Earth MOID | data51 = | label52 = Mercury MOID | data52 = | label53 = Venus MOID | data53 = | label54 = Mars MOID | data54 = | label55 = Jupiter MOID | data55 = 0.2752 AU | label56 = Saturn MOID | data56 = | label57 = Uranus MOID | data57 = | label58 = Neptune MOID | data58 = | label59 = T_Jupiter | data59 = 2.8990

| header60 = Proper orbital elements

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

| label71 = Dimensions | data71 = Template:Val Template:Small<ref name="Marchis-2014" />
Template:Val<ref name="Storrs-1999" /> | label72 = Template:Longitem | data72 = Template:Val<ref name="Marchis-2014" />
(if bilobe: Template:Val)<ref name="Marchis-2014" />
Template:Val<ref name="jpldata" />
Template:Val<ref name="Grav-2012" />
Template:Val<ref name="Carry-2012" />
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Template:Val<ref name="Carry-2012" />
Template:Val<ref name="Descamps-2015" /> | label82 = Template:Longitem | data82 = | label83 = Template:Longitem | data83 = | label84 = Template:Longitem | data84 = | label85 = Template:Longitem | data85 = Template:Convert<ref name="Marchis-2014" /> | 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 = 0.025<ref name="jpldata" />
Template:Val<ref name="AKARI" />
Template:Val<ref name="Grav-2012" /> | label94 = Temperature | data94 =

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624 Hektor Template:IPAc-en is the largest Jupiter trojan and the namesake of the Hektor family, with a highly elongated shape equivalent in volume to a sphere of approximately 225 to 250 kilometers diameter. It was discovered on 10 February 1907, by astronomer August Kopff at Heidelberg Observatory in southwest Germany, and named after the Trojan prince Hector, from Greek mythology.<ref name="MPC-object" /><ref name="springer" /> It has one small 12-kilometer sized satellite, Skamandrios, discovered in 2006.<ref name="Marchis-2014" />

DescriptionEdit

Hektor is a D-type asteroid, dark and reddish in colour. It lies in Jupiter's leading Lagrangian point, Template:L4, called the Greek camp after one of the two sides in the legendary Trojan War. Hektor is named after the Trojan hero Hektor and is thus one of two trojan asteroids that is "misplaced" in the wrong camp (the other one being 617 Patroclus in the Trojan camp).

Contact-binary hypothesisEdit

File:624 Hektor.png

Modelled shape of 624 Hektor from its light curve.

Hektor is one of the most elongated bodies of its size in the Solar System, being approximately 403 km in its longest dimension, but averaging only around 201 km in its other dimensions, with a total volume equivalent to an approx 250 km diameter sphere, and an estimated mass of Template:Val (thus density of 1.0g/cm³). It is thought that Hektor might be a contact binary (two asteroids joined by gravitational attraction) like 216 Kleopatra, composed of two more rounded lobes of 220 and 183 km mean diameters.<ref name="Marchis-2014" /> Hubble Space Telescope observations of Hektor in 1993 did not show an obvious bilobate shape because of a limited angular resolution. On 17 July 2006, the Keck 10-meter-II-telescope and its laser guide star adaptive optics (AO) system indicated a bilobate shape for Hektor,<ref name="Marchis-LGS" /> which was reinforced by later studies that, together with multiple historical lightcurves, suggest a rotation period of 6.9205 hours.<ref name="Marchis-2014" />

SatelliteEdit

Template:Redirect {{#invoke:infobox|infoboxTemplate | class = vcard | titleclass = fn org | title = Skamandrios | image = {{#invoke:InfoboxImage|InfoboxImage|image=|upright={{#if:||1.1}}|alt=}} | caption = | headerstyle = {{#if:|background-color:|background-color:#E0CCFF}} | labelstyle = max-width:{{#if:||11em}}; | autoheaders = y

| header1 = Discovery<ref name="Marchis-2014" />

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

| header20 = Orbital characteristics{{#ifeq:|yes| (barycentric)}}<ref name="Marchis-2014" />

| data21 = | data22 = {{#if: |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 = Template:Val | label33 = Template:Longitem | data33 = | label34 = Eccentricity | data34 = Template:Val | label35 = Template:Longitem | data35 = Template:Val days | label36 = Template:Longitem | data36 = | label37 = Template:Longitem | data37 = | label38 = Template:Longitem | data38 = | label39 = Template:Longitem | data39 = | label40 = Inclination | data40 = Template:Val (to primary)
Template:Val (in EQJ2000) | label41 = Template:Longitem | data41 = | label42 = Template:Longitem | data42 = Template:Val (in EQJ2000) | label43 = Template:Longitem | data43 = | label44 = Template:Longitem | data44 = | label45 = Template:Longitem | data45 = Template:Val (in EQJ2000) | 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 = | 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 = | label72 = Template:Longitem | data72 = Template:Val (assuming composition of primary) | 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 = | 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: |Template:Longitem |Albedo}} | data93 = | label94 = Temperature | data94 =

| data100 = {{#if:|

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

}}

| header110 = Atmosphere

| 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 }} A 10–15-km-diameter moon, named Skamandrios, was detected orbiting 624 Hektor in 2006 with a semi-major axis of 623.5 km and an orbital period of 2.9651 days (71.162 hours).<ref name=IAUC8732 /><ref name="Marchis-2014" /> It was confirmed with Keck observations in November 2011,<ref name="Marchis-tweet" /> and was then named on 12 March 2017.<ref name="MPC103967"/> No mass estimate was provided, but the equivalent volume suggests an approximate mass of Template:Val if the two bodies are of the same density. Its orbit is highly inclined and eccentric, and it is likely that its rotation is chaotic. Marchis et al. (2014) speculate that it was ejected after a low-velocity collision produced the bilobed primary. The newly merged primary could have spun fast enough to be unstable and shed some mass.<ref name="Marchis-2014" /> The dynamics of Skamandrios can be modeled by the restricted four-body problem.<ref>Template:Cite journal</ref>

Hektor is the first known trojan with a satellite companion and, so far, one of only four known binary trojan asteroids in the Template:L4 group (the others being 16974 Iphthime, 3548 Eurybates, and 15094 Polymele). 617 Patroclus, another large trojan asteroid of the Template:L5 group, consists of two almost equal-sized components.<ref name="Marchis-LGS" /> Two other binary asteroids are known in the L5 group, Template:Mpl and 29314 Eurydamas.<ref name="Johnson's Archive" />

StudiesEdit

624 Hektor was in a 2003 study of asteroids using the Hubble FGS.<ref name="Tanga-2003" /> Asteroids studied include 63 Ausonia, 15 Eunomia, 43 Ariadne, 44 Nysa, and 624 Hektor.<ref name="Tanga-2003" /> It has since been revisited several times, particularly as a test of the upgraded resolution of the Keck Observatory's LGS Adaptive Optics system which allowed Earth-based observation of binary asteroids for the first time.<ref name="Marchis-LGS" /><ref name="Marchis-2014" /> The asteroid has also been imaged by the NEOWISE and AKARI all-sky studies, which reported highly divergent size estimates of 147.4<ref name="Grav-2012" /> and 231.0 kilometers,<ref name="AKARI" /> respectively. This mostly arises from large differences in estimated albedo (approximately 0.107 for NEOWISE, and a much lower 0.034 for AKARI) rather than its absolute magnitude being measured only briefly at opposing extremes of a widely varying cycle such as thought to account for the uncertainty over the size of 1173 Anchises (624 Hektor's own abs. mag. recorded as a relatively similar 7.20 and 7.49 by the two studies). It is, unusually, not included in the published IRAS results, and is therefore the largest Jupiter trojan to be omitted from that study.

ReferencesEdit

Template:Reflist

External linksEdit

Keck image of Hektor and moon (Marchis 2011-Nov-11)
Distant Asteroid Revealed to be a Complex Mini Geological World (2014 February 27)
Asteroids with Satellites, Robert Johnston, johnstonsarchive.net
Template:AstDys
Template:JPL small body

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