Editing 624 Hektor

{{Short description|Largest Jupiter trojan}}
{{Use dmy dates|date=June 2018}}
{{Infobox planet
 | minorplanet     = yes
 | name            = 624 Hektor
 | background      = #C2FFFF
 | image           = Hektor & Skamandrios 2006 Jul 16.PNG
 | image_scale      =
 | caption         = 624 Hektor and its moon Skamandrios
 | discovery_ref   = &thinsp;<ref name="MPC-object" />
 | discoverer      = [[August Kopff|A. Kopff]]
 | discovery_site  = [[Heidelberg Observatory|Heidelberg Obs.]]
 | discovered      = 10 February 1907
 | mpc_name        = (624) Hektor
 | alt_names       = 1907 XM; 1948 VD
 | pronounced      = {{IPAc-en|ˈ|h|ɛ|k|t|ər}}<ref name=OED>{{OED|Hector}}</ref>
 | adjectives      = Hektorean or Hektorian <br />(both {{IPAc-en|h|ɛ|k|ˈ|t|oʊr|i|ə|n}})<ref name=OED/>
 | named_after     = [[Hector]] {{small|(Greek mythology)}}<ref name="springer" />
 | mp_category     = {{nowrap|[[Jupiter trojan]]&thinsp;<ref name="MPC-object" /><ref name="jpldata" />{{·}}[[Hektor family|Hektor]]&thinsp;<ref name="Ferret" />}}<br />{{mpcat|Greeks}}<ref name="MPC-Jupiter-Trojans" />
 | orbit_ref       = &thinsp;<ref name="jpldata" />
 | epoch           = 23 March 2018 ([[Julian day|JD]] 2458200.5)
 | uncertainty     = 0
 | observation_arc = 111.28 [[Julian year (astronomy)|yr]] (40,646 d)
 | aphelion        = 5.3824 [[Astronomical unit|AU]]
 | perihelion      = 5.1319 AU
 | semimajor       = 5.2571 AU
 | eccentricity    = 0.0238
 | period          = 12.05 yr (4,403 d)
 | mean_anomaly    = 136.09[[Degree (angle)|°]]
 | mean_motion     = {{Deg2DMS|0.0818|sup=ms}} / day
 | inclination     = 18.166°
 | asc_node        = 342.79°
 | arg_peri        = 185.22°
 | jupiter_moid    = 0.2752 AU
 | tisserand       = 2.8990
 | satellites      = 1 
 | dimensions      = {{val|403|x|201|u=km}} {{small|(derived)}}<ref name="Marchis-2014" /><br />{{val|370|x|195|x|195|u=km}}<ref name="Storrs-1999" />
 | mean_diameter   = {{val|250|26|u=km}}<ref name="Marchis-2014" /><br />(<small>if bilobe:</small> {{val|256|12|u=km}})<ref name="Marchis-2014" /><br />{{val|225|u=km}}<ref name="jpldata" /><br />{{val|147|2|u=km}}<ref name="Grav-2012" /><br />{{val|227|15|u=km}}<ref name="Carry-2012" /><br />{{val|231|4|u=km}}<ref name="AKARI" />
 | mass            = {{val|7.9|1.4|e=18|u=kg}}<ref name="Marchis-2014" /><br />{{val|9.95|0.12|e=18|u=kg}}<ref name="Carry-2012"/>
 | density         = {{val|1.0|0.3|u=g/cm3}}<ref name="Marchis-2014" /><br />{{val|1.63|0.32|u=g/cm3}}<ref name="Carry-2012" /><br />{{val|2.43|0.35|u=g/cm3}}<ref name="Descamps-2015" />
 | rotation        = {{convert|6.9205|h|d}}<ref name="Marchis-2014" />
 | albedo          = 0.025<ref name="jpldata" /><br />{{val|0.034|0.001}}<ref name="AKARI" /><br />{{val|0.107|0.011}}<ref name="Grav-2012" />
 | angular_size    = 0.078"<!-- Horizons 1955-Mar-17 --> to 0.048"  {{citation needed|date=March 2018}}
 | spectral_type   = [[D-type asteroid|D]] {{small|([[Tholen classification|Tholen]])}}<ref name="jpldata" />
 | magnitude       = 13.79 <!-- Horizons 1955-Mar-17 --> to 15.26  {{citation needed|date=March 2018}}
 | abs_magnitude   = 7.20<ref name="Grav-2012" />{{·}}7.3<ref name="jpldata" />{{·}}7.49<ref name="AKARI" />
}}

'''624 Hektor''' {{IPAc-en|ˈ|h|ɛ|k|t|ər}} 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 [[Minor-planet moon|satellite]], [[#Satellite|Skamandrios]], discovered in 2006.<ref name="Marchis-2014" />

== Description ==
Hektor is a [[D-type asteroid]], dark and reddish in colour. It lies in Jupiter's leading [[Lagrangian point]], {{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&nbsp;Patroclus]] in the [[Trojan camp]]).

== Contact-binary hypothesis ==
[[File:624 Hektor.png|thumb|left| 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&nbsp;km in its longest dimension, but averaging only around 201&nbsp;km in its other dimensions, with a total volume equivalent to an approx 250&nbsp;km diameter sphere, and an estimated mass of {{val|7.9|e=18|u=kg}} (thus density of 1.0g/cm<sup>3</sup>). It is thought that Hektor might be a [[contact binary (asteroid)|contact binary]] (two asteroids joined by gravitational attraction) like [[216 Kleopatra]], composed of two more rounded lobes of 220 and 183&nbsp;km mean diameters.<ref name="Marchis-2014" /> [[Hubble Space Telescope]] observations of Hektor in 1993 did not show an obvious [[wikt:bilobate|bilobate]] shape because of a limited [[angular resolution]]. On 17 July 2006, the [[Keck telescopes|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" />

==Satellite==
{{Redirect|Skamandrios (moon)|the mythological figure|Skamandrios (disambiguation){{!}}Scamandrius}}
{{Infobox planet
| name                   = Skamandrios
| image                  = 
| caption                = 
| background             = <!-- #FFFFC0 -->
| discovery_ref          = <ref name="Marchis-2014" />
| discoverer             = Marchis et al.
| discovered             = 2006 July 16
| mpc_name               = Hektor I
| pronounced             = {{IPAc-en|s|k|ə|ˈ|m|æ|n|d|r|i|ə|s}}
| named_after            = [[Astyanax|Scamandrius]]
| alt_names              = {{mp|S/2006 (624) 1}}
| adjectives             = Skamandrian
| orbit_ref              = <ref name="Marchis-2014" />
| epoch                  = 
| semimajor              = {{val|623.5|10|u=km}}
| eccentricity           = {{val|0.31|0.03}}
| period                 = {{val|2.9651|0.0003}} days
| mean_anomaly           = 
| inclination            = {{val|50.1|1.1|u=°}} (to primary)<br />{{val|166.2|3.2|u=°}} (in EQJ2000)
| angular_dist           = 
| asc_node               = {{val|170.7|6.1|u=°}} (in EQJ2000)
| arg_peri               = {{val|113.4|1.4|u=°}} (in EQJ2000)
| satellite_of           = 
| mean_diameter          = {{val|12|3|u=km}} (assuming composition of primary)
| mass                   = 
| density                = 
| albedo                 = 
| spectral_type          = 
| magnitude              = 
| abs_magnitude          = 
}}
A 10–15-km-diameter moon, named '''Skamandrios''', was detected orbiting 624 Hektor in 2006 with a semi-major axis of 623.5&nbsp;km and an orbital period of 2.9651&nbsp;days (71.162&nbsp;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 {{val|8.74|e=14|u=kg}} 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 [[n-body problem|four-body problem]].<ref>{{cite journal | last1=Burgos-García | first1=Jaime | last2=Celletti | first2=Alessandra | last3=Gales | first3=Catalin | last4=Gidea | first4=Marian | last5=Lam | first5=Wai-Ting | title=Hill Four-Body Problem with Oblate Bodies: An Application to the Sun–Jupiter–Hektor–Skamandrios System | journal=Journal of Nonlinear Science | publisher=Springer Science and Business Media LLC | volume=30 | issue=6 | date=2020-07-16 | issn=0938-8974 | doi=10.1007/s00332-020-09640-x | pages=2925–2970| bibcode=2020JNS....30.2925B | s2cid=225526961 }}</ref>

Hektor is the first known trojan with a satellite companion and, so far, one of only four known binary trojan asteroids in the {{L4}} group (the others being [[16974 Iphthime]], [[3548 Eurybates]], and [[15094 Polymele]]).
[[617 Patroclus]], another large trojan asteroid of the {{L5}} group, consists of two almost equal-sized components.<ref name="Marchis-LGS" /> Two other binary asteroids are known in the L5 group, {{mpl|(17365) 1978 VF|11}} and [[29314 Eurydamas]].<ref name="Johnson's Archive" />

== Studies ==
624 Hektor was in a 2003 study of asteroids using the Hubble [[Fine Guidance Sensor (HST)|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&nbsp;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.

== References ==
{{reflist|refs=

<ref name="jpldata">{{cite web
  |type       = 2018-05-25 last obs.
  |title      = JPL Small-Body Database Browser: 624 Hektor (1907 XM)
  |url        = https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2000624
  |publisher  = [[Jet Propulsion Laboratory]]
  |access-date = 14 June 2018}}</ref>

<ref name="MPC-object">{{cite web
  |title      = 624 Hektor (1907 XM)
  |work       = Minor Planet Center
  |url        = https://www.minorplanetcenter.net/db_search/show_object?object_id=624
  |access-date = 14 June 2018}}</ref>

<ref name="springer">{{cite book
  |last       = Schmadel | first = Lutz D.
  |title = Dictionary of Minor Planet Names |publisher  = Springer Berlin Heidelberg
  |page       = 63
  |date       = 2007
  |isbn       = 978-3-540-00238-3
  |doi       = 10.1007/978-3-540-29925-7_625 |chapter       = (624) Hektor }}</ref>

<ref name="Grav-2012">{{cite journal
  |first1     = T. |last1 = Grav
  |first2     = A. K. |last2 = Mainzer
  |first3     = J. M. |last3 = Bauer
  |first4     = J. R. |last4 = Masiero
  |first5     = C. R. |last5 = Nugent
  |date       = November 2012
  |title      = WISE/NEOWISE Observations of the Jovian Trojan Population: Taxonomy
  |journal    = The Astrophysical Journal
  |volume     = 759
  |issue      = 1
  |page       = 10
  |bibcode    = 2012ApJ...759...49G
  |doi        = 10.1088/0004-637X/759/1/49
  |arxiv      = 1209.1549
  |s2cid = 119101711
 }} ([http://vizier.cfa.harvard.edu/viz-bin/VizieR-6?-source=J/ApJ/759/49/table1&MPC=00624 online catalog])</ref>

<ref name="MPC-Jupiter-Trojans">{{cite web
  |title      = List of Jupiter Trojans
  |work       = Minor Planet Center
  |date       = 4 October 2017
  |url        = https://www.minorplanetcenter.net/iau/lists/JupiterTrojans.html
  |access-date = 19 October 2017}}</ref>

<ref name="Ferret">{{cite web
  |title      = Asteroid 624 Hektor – Nesvorny HCM Asteroid Families V3.0
  |work      = Small Bodies Data Ferret
  |url      = https://sbntools.psi.edu/ferret/SimpleSearch/results.action?targetName=624+Hektor
  |access-date      = 24 October 2019
  |archive-date      = 24 July 2020
  |archive-url      = https://web.archive.org/web/20200724200307/https://sbntools.psi.edu/ferret/SimpleSearch/results.action?targetName=624+Hektor
  |url-status      = dead
  }}</ref>

<ref name="Storrs-1999">{{Cite journal
  |display-authors = 6
  |first1     = Alex |last1 = Storrs
  |first2     = Ben |last2 = Weiss
  |first3     = Ben |last3 = Zellner
  |first4     = Win |last4 = Burleson
  |first5     = Rukmini |last5 = Sichitiu
  |first6     = Eddie |last6 = Wells
  |first7     = Charles |last7 = Kowal
  |first8     = David |last8 = Tholen
  |s2cid = 274199 |date       = February 1999
  |title      = Imaging Observations of Asteroids with Hubble Space Telescope
  |journal    = Icarus
  |volume     = 137
  |issue      = 2
  |pages      = 260–268
  |bibcode    = 1999Icar..137..260S
  |doi        = 10.1006/icar.1999.6047
  }}</ref>

<ref name="Carry-2012">{{Citation
  |first1     = B.
  |last1      = Carry
  |date       = December 2012
  |title      = Density of asteroids
  |journal       = Planetary and Space Science
  |volume     = 73
  |issue      = 1
  |pages      = 98–118
  |doi        = 10.1016/j.pss.2012.03.009
  |bibcode    = 2012P&SS...73...98C
  |arxiv      = 1203.4336 |s2cid = 119226456
 }} See Table 1.</ref>

<ref name="Marchis-2014">{{Cite journal
  |display-authors = 6
  |first1     = F. |last1 = Marchis
  |first2     = J. |last2 = Durech
  |first3     = J. |last3 = Castillo-Rogez
  |first4     = F. |last4 = Vachier
  |first5     = M. |last5 = Cuk
  |first6     = J. |last6 = Berthier
  |first7     = M. H. |last7 = Wong
  |first8     = P. |last8 = Kalas
  |first9     = G. |last9 = Duchene
  |first10    = M. A. |last10 = van Dam
  |first11    = H. |last11 = Hamanowa
  |first12    = M. |last12 = Viikinkoski
  |date       = March 2014
  |title      = The Puzzling Mutual Orbit of the Binary Trojan Asteroid (624) Hektor
  |journal    = The Astrophysical Journal Letters
  |volume     = 783
  |issue      = 2
  |page       = 6
  |bibcode    = 2014ApJ...783L..37M
  |doi        = 10.1088/2041-8205/783/2/L37
  |arxiv      = 1402.7336
  |s2cid = 19868908 }}</ref>

<ref name="Descamps-2015">{{Cite journal
  |last1      = Descamps
  |first1     = Pascal
  |date       = January 2015
  |title      = Dumb-bell-shaped equilibrium figures for fiducial contact-binary asteroids and EKBOs
  |journal    = Icarus
  |volume     = 245
  |pages      = 64–79
  |bibcode    = 2015Icar..245...64D
  |doi        = 10.1016/j.icarus.2014.08.002
  |arxiv      = 1410.7962
  |s2cid = 119272485
 }}</ref>

<ref name="AKARI">{{cite journal
  |display-authors = 6
  |first1     = Fumihiko |last1 = Usui
  |first2     = Daisuke |last2 = Kuroda
  |first3     = Thomas G. |last3 = Müller
  |first4     = Sunao |last4 = Hasegawa
  |first5     = Masateru |last5 = Ishiguro
  |first6     = Takafumi |last6 = Ootsubo
  |first7     = Daisuke |last7 = Ishihara
  |first8     = Hirokazu |last8 = Kataza
  |first9     = Satoshi |last9 = Takita
  |first10    = Shinki |last10 = Oyabu
  |first11    = Munetaka |last11 = Ueno
  |first12    = Hideo |last12 = Matsuhara
  |first13    = Takashi |last13 = Onaka
  |date       = October 2011
  |title      = Asteroid Catalog Using Akari: AKARI/IRC Mid-Infrared Asteroid Survey
  |journal    = Publications of the Astronomical Society of Japan
  |volume     = 63
  |issue      = 5
  |pages      = 1117–1138
  |bibcode    = 2011PASJ...63.1117U
  |doi        = 10.1093/pasj/63.5.1117
  |doi-access= 
  }} ([http://vizier.cfa.harvard.edu/viz-bin/VizieR-5?-source=J/PASJ/63/1117/acua_v1&Num=624 online], [https://core.ac.uk/download/pdf/43545172.pdf AcuA catalog p. 153])</ref>

<ref name="Tanga-2003">{{Cite journal
  |first1     = P. |last1 = Tanga
  |first2     = D. |last2 = Hestroffer
  |first3     = A. |last3 = Cellino
  |first4     = M. |last4 = Lattanzi
  |first5     = M. |last5 = Di Martino
  |first6     = V. |last6 = Zappalà
  |date       = April 2003
  |title      = Asteroid observations with the Hubble Space Telescope. II. Duplicity search and size measurements for 6 asteroids
  |url        = https://www.aanda.org/articles/aa/pdf/2003/14/aa3023.pdf
  |journal    = Astronomy and Astrophysics
  |volume = 401
  |issue = 2
  |pages      = 733–741
  |bibcode    = 2003A&A...401..733T
  |doi        = 10.1051/0004-6361:20030032
  |access-date= 14 June 2018|doi-access= free
  }}</ref>

<ref name="Marchis-LGS">{{cite web
 |author       = Franck Marchis
 |title        = Searching and Characterizing Multiple Trojan Asteroids with LGS AO Systems
 |date         = November 2005
 |type         = PDF
 |url          = http://www.mpia-hd.mpg.de/PARSEC/Ring2007/TalksPostersPDF/Friday/TrojanAsteroids_FranckMarchis.pdf
 |access-date  = 14 June 2018
 |archive-date = 28 July 2020
 |archive-url  = https://web.archive.org/web/20200728125057/https://www2.mpia-hd.mpg.de/PARSEC/Ring2007/TalksPostersPDF/Friday/TrojanAsteroids_FranckMarchis.pdf
 |url-status   = dead
}}</ref>

<ref name=IAUC8732>{{cite web
  |title      = IAUC 8732: S/2006 (624) 1 (Satellite Discovery)
  |date       = 21 July 2006
  |work       = Central Bureau for Astronomical Telegrams
  |publisher  = International Astronomical Union
  |url        = http://www.cbat.eps.harvard.edu/iauc/08700/08732.html
  |access-date = 14 June 2018}}</ref>

<ref name="Marchis-tweet">{{cite tweet
  |number    = 135034306958606336
  |user      = AllPlanets
  |title     = Dome closed, Keck telescope is...
  |date      = 11 November 2011}}</ref>

<ref name="MPC103967">{{cite web
  |title      = M.P.C. 103967
  |url        = https://minorplanetcenter.net/iau/ECS/MPCArchive/2017/MPC_20170312.pdf
  |work       = Minor Planet Circular
  |publisher  = Minor Planet Center
  |date       = 12 March 2017
  |access-date = 15 October 2020}}</ref>

<ref name="Johnson's Archive">{{cite web
  |title      = Johnson's Archive - asteroids with satellites
  |url        = http://www.johnstonsarchive.net/astro/asteroidmoons.html#1
  |access-date = 25 October 2020}}</ref>

}} <!-- end of reflist -->

== External links ==
* [https://twitter.com/?photo_id=1#!/AllPlanets/status/135034306958606336/photo/1 Keck image of Hektor and moon] (Marchis 2011-Nov-11)
* [https://web.archive.org/web/20140303204210/http://www.keckobservatory.org/recent/entry/distant_asteroid_revealed_to_be_a_complex_mini_geological_world Distant Asteroid Revealed to be a Complex Mini Geological World] (2014 February 27)
* [http://www.johnstonsarchive.net/astro/asteroidmoons.html Asteroids with Satellites], Robert Johnston, johnstonsarchive.net
* {{AstDys|624}}
* {{JPL small body}}

{{Minor planets navigator |623 Chimaera |number=624 |625 Xenia}}
{{Large asteroids}}
{{Authority control}}

{{DEFAULTSORT:Hektor}}
[[Category:Jupiter trojans (Greek camp)|000624]]
[[Category:Hektor asteroids|000624]]
[[Category:Discoveries by August Kopff]]
[[Category:Named minor planets]]
[[Category:Binary asteroids|000624]]
[[Category:Contact binary (small Solar System body)|000624]]
[[Category:D-type asteroids (Tholen)|000624]]
[[Category:Astronomical objects discovered in 1907|19070210]]