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⚫
{{Short description|Largest Jupiter trojan}}
⚫
{{Use dmy dates|date=June 2018}}
{{Infobox planet
{{Infobox planet
| minorplanet = yes
| minorplanet = yes
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| background = #C2FFFF
| background = #C2FFFF
| image = Hektor & Skamandrios 2006 Jul 16.PNG
| image = Hektor & Skamandrios 2006 Jul 16.PNG
| image_size = 240
| image_scale =
| caption = 624 Hektor and its moon Skamandrios
| caption = 624 Hektor and its moon Skamandrios
| discovery_ref = &thinsp;<ref name="MPC-object" />
| discovery_ref = &thinsp;<ref name="MPC-object" />
Line 13: Line 15:
| alt_names = 1907 XM; 1948 VD
| alt_names = 1907 XM; 1948 VD
| pronounced = {{IPAc-en|ˈ|h|ɛ|k|t|ər}}<ref name=OED>{{OED|Hector}}</ref>
| 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/>
| 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" />
| 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 />{{small|([[Greek camp]])}}<ref name="MPC-Jupiter-Trojans" />
| 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" />
| orbit_ref = &thinsp;<ref name="jpldata" />
| epoch = 23 March 2018 ([[Julian day|JD]] 2458200.5)
| epoch = 23 March 2018 ([[Julian day|JD]] 2458200.5)
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| tisserand = 2.8990
| tisserand = 2.8990
| satellites = 1
| 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" />
| 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" />
| 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"/>
| 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" />
| 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" />
| rotation = {{convert|6.9205|h|d}}<ref name="Marchis-2014" />
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}}
}}


'''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]], [[#Contact binary plus moon|Skamandrios]], discovered in 2006.
'''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 ==
== 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]]).
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 ==
== 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" />
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" />

⚫
Hektor is, so far, one of only three known binary trojan asteroids in the {{L4}} point (the others being [[16974 Iphthime]] and [[3548 Eurybates]]) and the first known trojan with a satellite companion. [[617 Patroclus]], another large trojan asteroid located in the {{L5}} point, is composed of two almost equal-sized components.<ref name="Marchis-LGS" /> There are now a further two known binary asteroids in the L5 point, [[(17365) 1978 VF11]] and [[29314 Eurydamas]].<ref name="Johnson's Archive" />


==Satellite==
==Satellite==
{{Redirect|Skamandrios (moon)|the mythological figure|Skamandrios}}
{{Redirect|Skamandrios (moon)|the mythological figure|Skamandrios (disambiguation){{!}}Scamandrius}}
{{Infobox planet
{{Infobox planet
| name = Skamandrios
| name = Skamandrios
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| mpc_name = Hektor I
| mpc_name = Hektor I
| pronounced = {{IPAc-en|s|k|ə|ˈ|m|æ|n|d|r|i|ə|s}}
| pronounced = {{IPAc-en|s|k|ə|ˈ|m|æ|n|d|r|i|ə|s}}
| named_after = [[Scamandrius]]
| named_after = [[Astyanax|Scamandrius]]
| alt_names = {{mp|S/2006 (624) 1}}
| alt_names = {{mp|S/2006 (624) 1}}
| adjectives = Skamandrian
| adjectives = Skamandrian
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| period = {{val|2.9651|0.0003}} days
| period = {{val|2.9651|0.0003}} days
| mean_anomaly =
| mean_anomaly =
| inclination = {{val|50.1|1.1|u=°}} (to primary)<br>{{val|166.2|3.2|u=°}} (in EQJ2000)
| inclination = {{val|50.1|1.1|u=°}} (to primary)<br />{{val|166.2|3.2|u=°}} (in EQJ2000)
| angular_dist =
| angular_dist =
| asc_node = {{val|170.7|6.1|u=°}} (in EQJ2000)
| asc_node = {{val|170.7|6.1|u=°}} (in EQJ2000)
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| abs_magnitude =
| abs_magnitude =
}}
}}
A 10–15-km-diameter moon, named '''Skamandrios''', was detected orbiting 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" />
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 ==
== 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, although 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.
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.

⚫
{{Largest Jupiter trojans}}

== See also ==
* {{section link|Asteroids in fiction|Other asteroids}}


== References ==
== References ==
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<ref name="springer">{{cite book
<ref name="springer">{{cite book
|title = Dictionary of Minor Planet Names – (624) Hektor
|last = Schmadel | first = Lutz D.
|last = Schmadel | first = Lutz D.
|publisher = Springer Berlin Heidelberg
|title = Dictionary of Minor Planet Names |publisher = Springer Berlin Heidelberg
|page = 63
|page = 63
|date = 2007
|date = 2007
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|doi = 10.1088/0004-637X/759/1/49
|doi = 10.1088/0004-637X/759/1/49
|arxiv = 1209.1549
|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>
}} ([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
<ref name="MPC-Jupiter-Trojans">{{cite web
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<ref name="Ferret">{{cite web
<ref name="Ferret">{{cite web
|title = Asteroid 624 Hektor – Nesvorny HCM Asteroid Families V3.0
|title = Asteroid 624 Hektor – Nesvorny HCM Asteroid Families V3.0
|work = Small Bodies Data Ferret
|work = Small Bodies Data Ferret
|url = https://sbntools.psi.edu/ferret/SimpleSearch/results.action?targetName=624+Hektor
|url = https://sbntools.psi.edu/ferret/SimpleSearch/results.action?targetName=624+Hektor
|access-date = 24 October 2019}}</ref>
|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
<ref name="Storrs-1999">{{Cite journal
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|doi = 10.1016/j.pss.2012.03.009
|doi = 10.1016/j.pss.2012.03.009
|bibcode = 2012P&SS...73...98C
|bibcode = 2012P&SS...73...98C
|arxiv = 1203.4336 }} See Table 1.</ref>
|arxiv = 1203.4336 |s2cid = 119226456
}} See Table 1.</ref>


<ref name="Marchis-2014">{{Cite journal
<ref name="Marchis-2014">{{Cite journal
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|doi = 10.1088/2041-8205/783/2/L37
|doi = 10.1088/2041-8205/783/2/L37
|arxiv = 1402.7336
|arxiv = 1402.7336
}}</ref>
|s2cid = 19868908 }}</ref>


<ref name="Descamps-2015">{{Cite journal
<ref name="Descamps-2015">{{Cite journal
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|doi = 10.1016/j.icarus.2014.08.002
|doi = 10.1016/j.icarus.2014.08.002
|arxiv = 1410.7962
|arxiv = 1410.7962
|s2cid = 119272485
⚫
}}</ref>
}}</ref>


<ref name="AKARI">{{cite journal
<ref name="AKARI">{{cite journal
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|bibcode = 2011PASJ...63.1117U
|bibcode = 2011PASJ...63.1117U
|doi = 10.1093/pasj/63.5.1117
|doi = 10.1093/pasj/63.5.1117
|doi-access= free
|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>
}} ([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>


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<ref name="Marchis-LGS">{{cite web
<ref name="Marchis-LGS">{{cite web
|author = Franck Marchis
|author = Franck Marchis
|title = Searching and Characterizing Multiple Trojan Asteroids with LGS AO Systems
|title = Searching and Characterizing Multiple Trojan Asteroids with LGS AO Systems
|date = November 2005
|date = November 2005
|type = PDF
|type = PDF
|url = http://www.mpia-hd.mpg.de/PARSEC/Ring2007/TalksPostersPDF/Friday/TrojanAsteroids_FranckMarchis.pdf
|url = http://www.mpia-hd.mpg.de/PARSEC/Ring2007/TalksPostersPDF/Friday/TrojanAsteroids_FranckMarchis.pdf
|access-date= 14 June 2018}}</ref>
|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
<ref name=IAUC8732>{{cite web
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* {{JPL small body}}
* {{JPL small body}}


⚫
{{Use dmy dates|date=June 2018}}
{{Minor planets navigator |623 Chimaera |number=624 |625 Xenia}}
{{Minor planets navigator |623 Chimaera |number=624 |625 Xenia}}
{{Large asteroids}}
{{Authority control}}


{{DEFAULTSORT:Hektor}}
{{DEFAULTSORT:Hektor}}
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[[Category:Hektor asteroids|000624]]
[[Category:Hektor asteroids|000624]]
[[Category:Discoveries by August Kopff]]
[[Category:Discoveries by August Kopff]]
[[Category:Minor planets named from Greek mythology]]
[[Category:Named minor planets]]
[[Category:Named minor planets]]
[[Category:Binary asteroids|000624]]
[[Category:Binary asteroids|000624]]

Latest revision as of 15:28, 28 September 2024

624 Hektor
624 Hektor and its moon Skamandrios
Discovery [1]
Discovered byA. Kopff
Discovery siteHeidelberg Obs.
Discovery date10 February 1907
Designations
(624) Hektor
Pronunciation/ˈhɛktər/[2]
Named after
Hector (Greek mythology)[3]
1907 XM; 1948 VD
Jupiter trojan [1][4] · Hektor [5]
Greeks Greeks[6]
AdjectivesHektorean or Hektorian
(both /hɛkˈtɔːriən/)[2]
Orbital characteristics [4]
Epoch 23 March 2018 (JD 2458200.5)
Uncertainty parameter 0
Observation arc111.28 yr (40,646 d)
Aphelion5.3824 AU
Perihelion5.1319 AU
5.2571 AU
Eccentricity0.0238
12.05 yr (4,403 d)
136.09°
0° 4m 54.48s / day
Inclination18.166°
342.79°
185.22°
Known satellites1
Jupiter MOID0.2752 AU
TJupiter2.8990
Physical characteristics
Dimensions403 km × 201 km (derived)[7]
370 km × 195 km × 195 km[8]
250±26 km[7]
(if bilobe: 256±12 km)[7]
225 km[4]
147±2 km[9]
227±15 km[10]
231±4 km[11]
Mass(7.9±1.4)×1018 kg[7]
(9.95±0.12)×1018 kg[10]
Mean density
1.0±0.3 g/cm3[7]
1.63±0.32 g/cm3[10]
2.43±0.35 g/cm3[12]
6.9205 hours (0.28835 d)[7]
0.025[4]
0.034±0.001[11]
0.107±0.011[9]
D (Tholen)[4]
13.79 to 15.26 [citation needed]
7.20[9] · 7.3[4] · 7.49[11]
0.078" to 0.048" [citation needed]

624 Hektor /ˈhɛktər/ 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.[1][3] It has one small 12-kilometer sized satellite, Skamandrios, discovered in 2006.[7]

Description

[edit]

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 Patroclus in the Trojan camp).

Contact-binary hypothesis

[edit]
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 7.9×1018 kg (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.[7] 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,[13] which was reinforced by later studies that, together with multiple historical lightcurves, suggest a rotation period of 6.9205 hours.[7]

Satellite

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"Skamandrios (moon)" redirects here. For the mythological figure, see Scamandrius.
Skamandrios
Discovery[7]
Discovered byMarchis et al.
Discovery date2006 July 16
Designations
Designation
Hektor I
Pronunciation/skəˈmændriəs/
Named after
Scamandrius
S/2006 (624) 1
AdjectivesSkamandrian
Orbital characteristics[7]
623.5±10 km
Eccentricity0.31±0.03
2.9651±0.0003 days
Inclination50.1°±1.1° (to primary)
166.2°±3.2° (in EQJ2000)
170.7°±6.1° (in EQJ2000)
113.4°±1.4° (in EQJ2000)
Physical characteristics
12±3 km (assuming composition of primary)

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).[14][7] It was confirmed with Keck observations in November 2011,[15] and was then named on 12 March 2017.[16] No mass estimate was provided, but the equivalent volume suggests an approximate mass of 8.74×1014 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.[7] The dynamics of Skamandrios can be modeled by the restricted four-body problem.[17]

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.[13] Two other binary asteroids are known in the L5 group, (17365) 1978 VF11 and 29314 Eurydamas.[18]

Studies

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624 Hektor was in a 2003 study of asteroids using the Hubble FGS.[19] Asteroids studied include 63 Ausonia, 15 Eunomia, 43 Ariadne, 44 Nysa, and 624 Hektor.[19] 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.[13][7] The asteroid has also been imaged by the NEOWISE and AKARI all-sky studies, which reported highly divergent size estimates of 147.4[9] and 231.0 kilometers,[11] 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

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  1. ^ a b c "624 Hektor (1907 XM)". Minor Planet Center. Retrieved 14 June 2018.
  2. ^ a b "Hector". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
  3. ^ a b Schmadel, Lutz D. (2007). "(624) Hektor". Dictionary of Minor Planet Names. Springer Berlin Heidelberg. p. 63. doi:10.1007/978-3-540-29925-7_625. ISBN 978-3-540-00238-3.
  4. ^ a b c d e f "JPL Small-Body Database Browser: 624 Hektor (1907 XM)" (2018-05-25 last obs.). Jet Propulsion Laboratory. Retrieved 14 June 2018.
  5. ^ "Asteroid 624 Hektor – Nesvorny HCM Asteroid Families V3.0". Small Bodies Data Ferret. Archived from the original on 24 July 2020. Retrieved 24 October 2019.
  6. ^ "List of Jupiter Trojans". Minor Planet Center. 4 October 2017. Retrieved 19 October 2017.
  7. ^ a b c d e f g h i j k l m n Marchis, F.; Durech, J.; Castillo-Rogez, J.; Vachier, F.; Cuk, M.; Berthier, J.; et al. (March 2014). "The Puzzling Mutual Orbit of the Binary Trojan Asteroid (624) Hektor". The Astrophysical Journal Letters. 783 (2): 6. arXiv:1402.7336. Bibcode:2014ApJ...783L..37M. doi:10.1088/2041-8205/783/2/L37. S2CID 19868908.
  8. ^ Storrs, Alex; Weiss, Ben; Zellner, Ben; Burleson, Win; Sichitiu, Rukmini; Wells, Eddie; et al. (February 1999). "Imaging Observations of Asteroids with Hubble Space Telescope". Icarus. 137 (2): 260–268. Bibcode:1999Icar..137..260S. doi:10.1006/icar.1999.6047. S2CID 274199.
  9. ^ a b c d Grav, T.; Mainzer, A. K.; Bauer, J. M.; Masiero, J. R.; Nugent, C. R. (November 2012). "WISE/NEOWISE Observations of the Jovian Trojan Population: Taxonomy". The Astrophysical Journal. 759 (1): 10. arXiv:1209.1549. Bibcode:2012ApJ...759...49G. doi:10.1088/0004-637X/759/1/49. S2CID 119101711. (online catalog)
  10. ^ a b c Carry, B. (December 2012), "Density of asteroids", Planetary and Space Science, 73 (1): 98–118, arXiv:1203.4336, Bibcode:2012P&SS...73...98C, doi:10.1016/j.pss.2012.03.009, S2CID 119226456 See Table 1.
  11. ^ a b c d Usui, Fumihiko; Kuroda, Daisuke; Müller, Thomas G.; Hasegawa, Sunao; Ishiguro, Masateru; Ootsubo, Takafumi; et al. (October 2011). "Asteroid Catalog Using Akari: AKARI/IRC Mid-Infrared Asteroid Survey". Publications of the Astronomical Society of Japan. 63 (5): 1117–1138. Bibcode:2011PASJ...63.1117U. doi:10.1093/pasj/63.5.1117. (online, AcuA catalog p. 153)
  12. ^ Descamps, Pascal (January 2015). "Dumb-bell-shaped equilibrium figures for fiducial contact-binary asteroids and EKBOs". Icarus. 245: 64–79. arXiv:1410.7962. Bibcode:2015Icar..245...64D. doi:10.1016/j.icarus.2014.08.002. S2CID 119272485.
  13. ^ a b c Franck Marchis (November 2005). "Searching and Characterizing Multiple Trojan Asteroids with LGS AO Systems" (PDF) (PDF). Archived from the original (PDF) on 28 July 2020. Retrieved 14 June 2018.
  14. ^ "IAUC 8732: S/2006 (624) 1 (Satellite Discovery)". Central Bureau for Astronomical Telegrams. International Astronomical Union. 21 July 2006. Retrieved 14 June 2018.
  15. ^ @AllPlanets (11 November 2011). "Dome closed, Keck telescope is..." (Tweet) – via Twitter.
  16. ^ "M.P.C. 103967" (PDF). Minor Planet Circular. Minor Planet Center. 12 March 2017. Retrieved 15 October 2020.
  17. ^ Burgos-García, Jaime; Celletti, Alessandra; Gales, Catalin; Gidea, Marian; Lam, Wai-Ting (16 July 2020). "Hill Four-Body Problem with Oblate Bodies: An Application to the Sun–Jupiter–Hektor–Skamandrios System". Journal of Nonlinear Science. 30 (6). Springer Science and Business Media LLC: 2925–2970. Bibcode:2020JNS....30.2925B. doi:10.1007/s00332-020-09640-x. ISSN 0938-8974. S2CID 225526961.
  18. ^ "Johnson's Archive - asteroids with satellites". Retrieved 25 October 2020.
  19. ^ a b Tanga, P.; Hestroffer, D.; Cellino, A.; Lattanzi, M.; Di Martino, M.; Zappalà, V. (April 2003). "Asteroid observations with the Hubble Space Telescope. II. Duplicity search and size measurements for 6 asteroids" (PDF). Astronomy and Astrophysics. 401 (2): 733–741. Bibcode:2003A&A...401..733T. doi:10.1051/0004-6361:20030032. Retrieved 14 June 2018.
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