617 Patroclus

From Wikipedia, the free encyclopedia
Jump to: navigation, search
617 Patroclus
Discovery [1]
Discovered by A. Kopff
Discovery site Heidelberg Obs.
Discovery date 17 October 1906
MPC designation (617) Patroclus
Pronunciation /pəˈtrkləs/ pə-TROH-kləs  
Named after
(Greek mythology)[2]
1906 VY · 1941 XC
1962 NB
Jupiter trojan[3]
(Trojan camp)[4]
Adjectives Patroclean
Orbital characteristics[1]
Epoch 16 February 2017 (JD 2457800.5)
Uncertainty parameter 0
Observation arc 19.15 yr (6,993 days)
Aphelion 5.9389 AU
Perihelion 4.4958 AU
5.2173 AU
Eccentricity 0.1383
11.92 yr (4,353 days)
0° 4m 57.72s / day
Inclination 22.047°
Known satellites 1 [5]
Jupiter MOID 0.1992 AU
TJupiter 2.8360
Physical characteristics
Dimensions Combined system effective size:
140.362±0.868 km[6]
140.92±4.7 km (IRAS:8)[7]
143.14±8.37 km (avg.)[8]
154 km equivalent diameter[9]

Patroclus alone: 127x117x98 km, 113 km equivalent diameter[9] (± 3 km)

Menoetius alone: 117x108x90 km, 104 km equivalent diameter[9] (± 3 km)
Volume 1.3636×103 km3[9]
Mass (1.36±0.11)×1018 kg[8]
1.20×1018 kg[9]
Mean density
0.88±0.17 g/cm3[8][9]
>40 h (dated)[10]
102.8 h[11]
102 h[12]
103.02±0.40 h[13]
103.5±0.3 h[14]
0.0471±0.003 (IRAS:8)[7]
Tholen = P[1] · P[15]
B–V = 0.677[1]
U–B = 0.215[1]

617 Patroclus (/pəˈtrkləs/ pə-TROH-kləs), provisional designation 1906 VY is a dark Jupiter trojan, slow rotator and binary system from the Trojan camp, of approximately 113 kilometers mean diameter. It was discovered on 17 October 1906, by German astronomer August Kopff at Heidelberg Observatory in southwest Germany; in 2001, its minor-planet moon, named Menoetius (/mɪˈnʃəs/ mi-NEE-shəs; official designation (617) Patroclus I Menoetius) was discovered. The satellite is slightly smaller than its primary, at approx 104 km mean diameter.

The asteroid was named after Patroclus from Greek mythology,[2][3] it was the second trojan to be discovered and the only member of the Trojan camp named after a Greek character.[5] It was also the first known binary system among the Trojans.[2] Patroclus is one of five Jupiter trojans targeted by the Lucy space probe.


Patroclus orbits in Jupiter's trailing Lagrangian point, L5,[5] in an area called the Trojan camp after one of the sides in the legendary Trojan War (the other node, at the L4 point, is called the "Greek camp").

It orbits the Sun at a distance of 4.5–5.9 AU once every 11 years and 11 months (4,353 days). Its orbit has an eccentricity of 0.14 and an inclination of 22° with respect to the ecliptic.[1] The asteroid's observation arc begins at the discovering Heidelberg Observatory in November 1906, about 3 weeks after its official discovery observation.[3]

Binary system[edit]

In 2001, it was discovered that Patroclus is a binary system, made up of two components with a minor-planet moon of roughly similar size.[5][18][19] It is one of 18 binary Trojan asteroids known to exist; in 2006, accurate measurements of the orbit from the Keck Laser guide star adaptive optics system were reported.[20]

It was estimated[21] that the two components orbit around their center of mass in 4.283±0.004 days at a distance of 680±20 km in a roughly circular orbit.[5] Combining these observations with thermal measurements taken in 2000, the sizes of the components of the system were estimated at 106 km and 98 km, with an equivalent whole-system diameter of 145 km[5], refined by later measurements from the Keck Observatory to approximately 122 km and 112 km for each partner[22], and a co-orbital period of 103.5±0.3 hours (4.3125±0.0125 days)[20][14].

More recent direct optical measurements using stellar occlusion data pin the orbital distance closer to 664.6km, and give a size for the slightly larger component, which retains the name Patroclus, as 124.6x98.2 km and overall volume equivalent to a 113 km sphere, with the smaller component, now named Menoetius after the legendary father of Patroclus, measuring 117.2x93.0 km with a volume equivalent to a 104 km diameter sphere[9]. It was previously known by the provisional designation S/2001 (617) 1, the whole-system volume estimate was revised upwards slightly, to the equivalent of a 154 km sphere.[dubious ]

Physical characteristics[edit]


Recent evidence suggests that the objects are icy like comets, rather than rocky like most asteroids; in the Tholen classification, Patroclus is a dark P-type asteroid.[15]

Because the density of the components (0.88 g/cm³) is less than water and about one third that of rock, it was suggested that the Patroclus system, previously thought to be a pair of rocky asteroids, is more similar to a comet in composition.[20] It is suspected that many Jupiter trojans are in fact small planetesimals captured in the Lagrange point of the Jupiter–Sun system during the migration of the giant planets 3.9 billion years ago. This scenario was proposed by A. Morbidelli and colleagues in a series of articles published in May 2005 in Nature.[23]


Since 1989, several rotational lightcurves of Patroclus have been obtained from photometric observations. Analysis of the best rated lightcurves gave a rotation period between 102.8 and 103.5 hours with a brightness amplitude of less than 0.1 magnitude (U=2/3/).[11][12][13][14] A low brightness variation typically indicates that a body has a nearly spheroidal shape, its long rotation period makes it a slow rotator.

Diameter and albedo[edit]

According to the surveys carried out by the Infrared Astronomical Satellite IRAS and NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, the Patroclus system has an effective combined size between 140.36 and 140.92 kilometers in diameter and its surface has an albedo of 0.047.[6][7] The Collaborative Asteroid Lightcurve Link adopts the results obtained by IRAS, that is, an albedo of 0.0471 and a diameter of 140.92 kilometers based on an absolute magnitude of 8.19.[15]

The largest Jupiter trojans
Trojan Diameter (km)
624 Hektor 225
617 Patroclus 140
911 Agamemnon 131
588 Achilles 130
3451 Mentor 126
3317 Paris 119
1867 Deiphobus 118
1172 Äneas 118
1437 Diomedes 118
1143 Odysseus 115
Source: JPL Small-Body Database, NEOWISE data


Patroclus is a proposed target for Lucy, a mission to several asteroids, mostly Jupiter trojans,[24] the mission's targets with their flyby dates are:[25][26]

  1. 52246 Donaldjohanson — 20 April 2025: 4 km diameter C-type asteroid in the inner main-belt, member of ~130Myr old Erigone family;
  2. 3548 Eurybates — 12 August 2027: 64 km diameter C-type Jupiter Trojan in the Greek camp at L4, largest member of the only confirmed disruptive collisional family in the Trojans;
  3. 15094 Polymele — 15 September 2027: 21 km diameter P-type Trojan at L4, likely collisional fragment;
  4. 11351 Leucus — 18 April 2028: 34 km diameter D-type slow rotator Trojan at L4;
  5. 21900 Orus — 11 November 2028: 51 km diameter D-type Trojan at L4;
  6. 617 Patroclus — 2 March 2033: P-type binary Trojan. The primary, Patroclus, has a mean diameter of 113 km and its companion, Menoetius, has a diameter of 104 km. The pair orbit at a separation of 680 km. The binary resides in the Trojan camp at L5.


This minor planet was named after the Greek hero Patroclus from Greek mythology. Friend of Achilles, he was killed by Hector during the Trojan War (see also (588) and (624)). The minor planet's name was proposed by Austrian astronomer Johann Palisa, the official naming citation was mentioned in The Names of the Minor Planets by Paul Herget in 1955 (H 65).[2]

Patroclus is the only object in the Trojan camp to be named after a Greek rather than a Trojan character. The naming conventions for the Jupiter trojans were not adopted until after Patroclus was named (similarly, the asteroid Hektor is the only Trojan character to appear in the Greek camp).


  1. ^ a b c d e f g "JPL Small-Body Database Browser: 617 Patroclus (1906 VY)" (2017-06-14 last obs.). Jet Propulsion Laboratory. Retrieved 11 July 2017. 
  2. ^ a b c d Schmadel, Lutz D. (2007). Dictionary of Minor Planet Names – (617) Patroclus. Springer Berlin Heidelberg. p. 62. ISBN 978-3-540-00238-3. Retrieved 11 July 2017. 
  3. ^ a b c "617 Patroclus (1906 VY)". Minor Planet Center. Retrieved 11 July 2017. 
  4. ^ "List of Jupiter Trojans". Minor Planet Center. 20 August 2016. Retrieved 11 July 2017. 
  5. ^ a b c d e f g Johnston, Wm. Robert (21 September 2014). "(617) Patroclus and Menoetius". johnstonsarchive.net. Retrieved 11 July 2017. 
  6. ^ a b c 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:1209.1549Freely accessible. Bibcode:2012ApJ...759...49G. doi:10.1088/0004-637X/759/1/49. Retrieved 11 July 2017. 
  7. ^ a b c d Tedesco, E. F.; Noah, P. V.; Noah, M.; Price, S. D. (October 2004). "IRAS Minor Planet Survey V6.0". NASA Planetary Data System. Bibcode:2004PDSS...12.....T. Retrieved 11 July 2017. 
  8. ^ a b c Carry, B. (December 2012), "Density of asteroids", Planetary and Space Science, 73, pp. 98–118, arXiv:1203.4336Freely accessible, Bibcode:2012P&SS...73...98C, doi:10.1016/j.pss.2012.03.009.  See Table 1.
  9. ^ a b c d e f g h Buie, Marc W.; Olkin, Catherine B.; Merline, William J.; Walsh, Kevin J.; Levison, Harold F.; Timerson, Brad; et al. (March 2015). "Size and Shape from Stellar Occultation Observations of the Double Jupiter Trojan Patroclus and Menoetius". The Astronomical Journal. 149 (3): 11. Bibcode:2015AJ....149..113B. doi:10.1088/0004-6256/149/3/113. Retrieved 11 July 2017. 
  10. ^ Gonano, M.; Mottola, S.; Neukum, G.; di Martino, M. (December 1990). "Physical study of outer belt asteroids". Space dust and debris; Proceedings of the Topical Meeting of the Interdisciplinary Scientific Commission B /Meetings B2: 197–200. Bibcode:1991AdSpR..11..197G. doi:10.1016/0273-1177(91)90563-Y. ISSN 0273-1177. Retrieved 11 July 2017. 
  11. ^ a b Marchis, Franck; Hestroffer, Daniel; Descamps, Pascal; Berthier, Jérô; me; Bouchez, Antonin H.; et al. (February 2006). "A low density of 0.8gcm-3 for the Trojan binary asteroid 617Patroclus". Nature. 439 (7076): 565–567.(NatureHomepage). arXiv:astro-ph/0602033Freely accessible. Bibcode:2006Natur.439..565M. doi:10.1038/nature04350. Retrieved 11 July 2017. 
  12. ^ a b Behrend, Raoul. "Asteroids and comets rotation curves – (617) Patroclus". Geneva Observatory. Retrieved 11 July 2017. 
  13. ^ a b Mueller, Michael; Marchis, Franck; Emery, Joshua P.; Harris, Alan W.; Mottola, Stefano; Hestroffer, Daniel; et al. (February 2010). "Eclipsing binary Trojan asteroid Patroclus: Thermal inertia from Spitzer observations". Icarus. 205 (2): 505–515. arXiv:0908.4198Freely accessible. Bibcode:2010Icar..205..505M. doi:10.1016/j.icarus.2009.07.043. Retrieved 11 July 2017. 
  14. ^ a b c Oey, Julian (July 2012). "Period Determination of 617 Patroclus". The Minor Planet Bulletin. 39 (3): 106–107. Bibcode:2012MPBu...39..106O. ISSN 1052-8091. Retrieved 11 July 2017. 
  15. ^ a b c d "LCDB Data for (617) Patroclus". Asteroid Lightcurve Database (LCDB). Retrieved 11 July 2017. 
  16. ^ Mainzer, A.; Grav, T.; Masiero, J.; Hand, E.; Bauer, J.; Tholen, D.; et al. (November 2011). "NEOWISE Studies of Spectrophotometrically Classified Asteroids: Preliminary Results" (PDF). The Astrophysical Journal. 741 (2): 25. arXiv:1109.6407Freely accessible. Bibcode:2011ApJ...741...90M. doi:10.1088/0004-637X/741/2/90. Retrieved 11 July 2017. 
  17. ^ 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. Retrieved 11 July 2017. 
  18. ^ Merline, W. J. (2001), IAUC 7741: 2001fc; S/2001 (617) 1; C/2001 T1, C/2001 T2 
  19. ^ "Satellites and Companions of Minor Planets". IAU / CBAT. 2009-09-17. Archived from the original on 2011-01-21. Retrieved 2011-01-25. 
  20. ^ a b c Marchis, F.; Hestroffer, D.; Descamps, P.; Berthier, J. R. M.; Bouchez, A. H.; Campbell, R. D.; Chin, J. C. Y.; Van Dam, M. A.; Hartman, S. K.; Johansson, E. M.; Lafon, R. E.; Le Mignant, D. L.; De Pater, I.; Stomski, P. J.; Summers, D. M.; Vachier, F. D. R.; Wizinovich, P. L.; Wong, M. H. (2006-02-02). "A low density of 0.8 g cm-3 for the Trojan binary asteroid 617 Patroclus". Nature. 439 (7076): 565–567. arXiv:astro-ph/0602033Freely accessible. Bibcode:2006Natur.439..565M. doi:10.1038/nature04350. PMID 16452974. 
  21. ^ Sanders, Robert (2006), Binary asteroid in Jupiter's orbit may be icy comet from solar system's infancy, University of California, Berkeley 
  22. ^ Sanders, Robert. "Trojan Binary Asteroid – Patroclus & Menoetius". UC Berkeley. Retrieved 2017-10-04. 
  23. ^ Morbidelli, A.; Levison, H. F.; Tsiganis, K.; Gomes, R. (2005-05-26). "Chaotic capture of Jupiter's Trojan asteroids in the early Solar System". Nature. 435 (7041): 462–465. Bibcode:2005Natur.435..462M. doi:10.1038/nature03540. PMID 15917801. 
  24. ^ Dreier, Casey; Lakdawalla, Emily (30 September 2015). "NASA announces five Discovery proposals selected for further study". The Planetary Society. Retrieved 2015-10-01. 
  25. ^ Levison, H. F.; Olkin, C.; Noll, K. S.; Marchi, S.; Lucy Team (March 2017). "Lucy: Surveying the Diversity of the Trojan Asteroids: The Fossils of Planet Formation" (PDF). 48th Lunar and Planetary Science Conference. Bibcode:2017LPI....48.2025L. Retrieved 13 April 2017. 
  26. ^ https://www.hou.usra.edu/meetings/lpsc2017/pdf/2025.pdf

External links[edit]