617 Patroclus

617 Patroclus
Discovery [1]
Discovered by A. Kopff
Discovery site Heidelberg Obs.
Discovery date 17 October 1906
Designations
MPC designation (617) Patroclus
Pronunciation /pəˈtroʊkləs/ pə-TROH-kləs  
Named after
 Patroclus
(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)
137.02°
0° 4m 57.72s / day
Inclination 22.047°
44.355°
308.37°
Known satellites 1 [5]
Jupiter MOID 0.1992 AU
Jupiter Tisserand parameter 2.8360
Physical characteristics
Dimensions 140.36±0.87 km[6]
140.362±0.868 km[7]
140.85±3.37 km[8]
140.92±4.7 km (IRAS:8)[9]
143.14±8.37 km (avg.)[10]
154 km[11]
Mass (1.36±0.11)×1018 kg[10]
Mean density
 0.88±0.17 g/cm3[10]
40 h (dated)[12]
102.8 h[13]
102 h[14]
103.02±0.40 h[15]
103.5±0.3 h[16]
0.047±0.003[6][7][8]
0.0471±0.003 (IRAS:8)[9]
Tholen = P [1] · P [17]
B–V = 0.677[1]
U–B = 0.215[1]
8.19[1][6][8][9][17]

    617 Patroclus (/pəˈtroʊkləs/ pə-TROH-kləs), provisional designation 1906 VY is a dark Jupiter trojan, slow rotator and binary system from the Trojan camp, approximately 140 kilometers in 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 (/mᵻˈniːʃəs/ mə-NEE-shəs; official designation (617) Patroclus I Menoetius) was discovered. The satellite is slightly smaller than its primary.

    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]

    Orbit

    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

    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 d 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. The slightly larger component, which measures 141 km in diameter, retains the name Patroclus.[5] The smaller component, measuring 112 km, is now named Menoetius,[5] after the legendary Patroclus's father. It was previously known by the provisional designation S/2001 (617) 1.

    Physical characteristics

    Composition

    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.[17]

    Because the density of the components (0.8 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.[22]

    Lightcurves

    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/).[13][14][15][16] 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

    According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the Japanese Akari satellite, and NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Patroclus measures between 140.36 and 140.92 kilometers in diameter and its surface has an albedo of 0.047.[6][7][8][9] 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.[17]

    The largest Jupiter trojans
    Trojan Diameter (km)
    624 Hektor 225
    911 Agamemnon 167
    1437 Diomedes 164
    1172 Äneas 143
    617 Patroclus 141
    588 Achilles 135
    1173 Anchises 126
    1143 Odysseus 126
    Source: JPL Small-Body Database, IRAS data

    Exploration

    Patroclus is a proposed target for Lucy, a mission to several asteroids, mostly Jupiter trojans.[23] The mission's targets with their flyby dates are:[24][25]

    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.

    Naming

    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).

    References

    1. 1 2 3 4 5 6 7 "JPL Small-Body Database Browser: 617 Patroclus (1906 VY)" (2017-06-14 last obs.). Jet Propulsion Laboratory. Retrieved 11 July 2017.
    2. 1 2 3 4 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. 1 2 3 "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. 1 2 3 4 5 6 7 Johnston, Wm. Robert (21 September 2014). "(617) Patroclus and Menoetius". johnstonsarchive.net. Retrieved 11 July 2017.
    6. 1 2 3 4 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. Bibcode:2011ApJ...741...90M. arXiv:1109.6407 Freely accessible. doi:10.1088/0004-637X/741/2/90. Retrieved 11 July 2017.
    7. 1 2 3 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. Bibcode:2012ApJ...759...49G. arXiv:1209.1549 Freely accessible. doi:10.1088/0004-637X/759/1/49. Retrieved 11 July 2017.
    8. 1 2 3 4 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" (PDF). 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.
    9. 1 2 3 4 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.
    10. 1 2 3 Carry, B. (December 2012), "Density of asteroids", Planetary and Space Science, 73, pp. 98–118, Bibcode:2012P&SS...73...98C, arXiv:1203.4336 Freely accessible, doi:10.1016/j.pss.2012.03.009. See Table 1.
    11. ↑ 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.
    12. ↑ 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. ISSN 0273-1177. doi:10.1016/0273-1177(91)90563-Y. Retrieved 11 July 2017.
    13. 1 2 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). Bibcode:2006Natur.439..565M. doi:10.1038/nature04350. Retrieved 11 July 2017.
    14. 1 2 Behrend, Raoul. "Asteroids and comets rotation curves – (617) Patroclus". Geneva Observatory. Retrieved 11 July 2017.
    15. 1 2 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. Bibcode:2010Icar..205..505M. doi:10.1016/j.icarus.2009.07.043. Retrieved 11 July 2017.
    16. 1 2 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.
    17. 1 2 3 4 "LCDB Data for (617) Patroclus". Asteroid Lightcurve Database (LCDB). 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. 1 2 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. Bibcode:2006Natur.439..565M. PMID 16452974. arXiv:astro-ph/0602033 Freely accessible. doi:10.1038/nature04350.
    21. ↑ Sanders, Robert (2006), Binary asteroid in Jupiter's orbit may be icy comet from solar system's infancy, University of California, Berkeley
    22. ↑ 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. PMID 15917801. doi:10.1038/nature03540.
    23. ↑ Dreier, Casey; Lakdawalla, Emily (30 September 2015). "NASA announces five Discovery proposals selected for further study". The Planetary Society. Retrieved 2015-10-01.
    24. ↑ 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.
    25. ↑ https://www.hou.usra.edu/meetings/lpsc2017/pdf/2025.pdf
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