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617 Patroclus

617 Patroclus (pə-troe'-kləs, how to say: /pəˈtroʊkləs/) is a binary minor planet made up of two similarly-sized objects orbiting their common centre of gravity. It is a Trojan, sharing an orbit with Jupiter. It was found in 1907 by August Kopff, and was the second Trojan asteroid to be found. Recent evidence suggests that the objects are icy comets, rather than rocky asteroids.

617 Patroclus
617 Patroclus Hubble.jpg
Hubble Space Telescope image composite of Patroclus and its companion Menoetius, taken in 2018
Discovery [1]
Discovered byA. Kopff
Discovery siteHeidelberg Obs.
Discovery date17 October 1906
Designations
MPC designation(617) Patroclus
Pronunciation/pəˈtroʊkləs/[7]
Named after
Πάτροκλος Patroklos
(Greek mythology)[2]
1906 VY · 1941 XC
1962 NB
Jupiter trojan [1][3][4]
Trojan [5][6] · background [6]
AdjectivesPatroclean /pætrəˈkliːən/[8]
Orbital characteristics [3]
Epoch 23 March 2018 (JD 2458200.5)
Uncertainty parameter 0
Observation arc19.15 yr (6,993 d)
Aphelion5.9376 AU
Perihelion4.4959 AU
5.2167 AU
Eccentricity0.1382
11.92 yr (4,352 d)
170.39°
0° 4m 57.72s / day
Inclination22.047°
44.354°
308.15°
Known satellites1 (Menoetius)[9]
Jupiter MOID0.1966 AU
TJupiter2.8360
Physical characteristics
Dimensions127 km × 117 km × 98 km (primary only)[10]
Mean diameter
113±3 km (primary only)[10]
140.36±0.87 km[11]
140.85±3.37 km[12]
140.92±4.7 km[13]
143.14±8.37 km[14]
154 km[10]
Volume1.36×106 km3[10]
Mass(1.36±0.11)×1018 kg[14]
1.20×1018 kg[10]
Mean density
0.88±0.17 g/cm3[14][10]
40 h (at least; dated)[15]
102.8 h[16]
102 h[17]
103.02±0.40 h[18]
103.5±0.3 h[19]
0.047±0.003[11][12][13]
D (Tholen)[20]
C0 (Barucci)[20]
D (Tedesco)[20]
U–B = 0.215±0.045[20]
B–V = 0.710±0.050[21]
V–R = 0.420±0.030[21]
V–I = 0.830±0.020[21]
8.19[3][11][12][13][4]

Orbit

Patroclus orbits in Jupiter's trailing Lagrangian point, L5, in an orbit called the 'Trojan node' after one of the sides in the legendary Trojan War (the other node is called the 'Greek node'). Patroclus is the only object in the Trojan camp to be named after a Greek character; the naming rules for the Trojan asteroids were not made until after Patroclus was named (similarly, the asteroid Hektor is the only Trojan character to appear in the Greek camp).

Binary

In 2001, it was found that Patroclus is a binary object, made up of two asteroids which are almost the same size. In February, 2006, a team of astronomers led by Franck Marchis measured accurately the orbit of the system using the Keck Laser guide star adaptive optics system. They thought[1] that the two asteroids orbit around their center of mass in 4.283±0.004 d at a distance of 680±20 km, describing a close to circular orbit. Putting together their sightings with thermal measurements taken in November 2000, the team thought what the size of the asteroids of the system could be. The slightly bigger asteroids, which measures 122 km in diameter, continues to have the name Patroclus. The smaller asteroid, measuring 112 km, is now named Menoetius (full name (617) Patroclus I Menoetius), after the legendary Patroclus's father. Its provisional designation was S/2001 (617) 1.

What they are made of

Because of the density of the asteroids (0.8 g/cm³) is less than water and about one third that of rock, the team of researchers led by F. Marchis suggest that the Patroclus system, previously thought to be a pair of rocky asteroids, is more similar to a comet in make up. It is thought that many Trojan asteroids are in fact small planetesimals captured in the Lagrange point of Jupiter-Sun system during the farther migration of the giant planets, 3.9 billion years ago. This scenario was suggested by A. Morbidelli and colleagues in a series of articles published in May 2005 in Nature journal.

617 Patroclus Media

  • Hubble images of Patroclus and Menoetius orbiting each other, from May to June 2017

  • Artist's conception of Patroclus and Menoetius orbiting around their center of mass, occasionally eclipsing one another

  • Artist's impression of the Patroclus-Menoetius binary system

  • Animation of Lucy's trajectory around Sun      Lucy ·        Sun ·        Earth ·        52246 Donaldjohanson  ·       3548 Eurybates ·        21900 Orus ·        617 Patroclus

  • Artist's impression of the Lucy spacecraft flying past the Patroclus-Menoetius system

Notes

  1. ^  UC-Berkeley press release on cometary origin

References

  1. ↑ 1.0 1.1 "617 Patroclus (1906 VY)". Minor Planet Center. Retrieved 13 June 2018.
  2. ↑ Schmadel, Lutz D. (2007). "(617) Patroclus". Dictionary of Minor Planet Names – (617) Patroclus. Springer Berlin Heidelberg. p. 62. doi:10.1007/978-3-540-29925-7_618. ISBN 978-3-540-00238-3.
  3. ↑ 3.0 3.1 3.2 "JPL Small-Body Database Browser: 617 Patroclus (1906 VY)" (2017-06-14 last obs.). Jet Propulsion Laboratory. Retrieved 13 June 2018.
  4. ↑ 4.0 4.1 "LCDB Data for (617) Patroclus". Asteroid Lightcurve Database (LCDB). Retrieved 11 July 2017.
  5. ↑ "List of Jupiter Trojans". Minor Planet Center. 20 August 2016. Retrieved 11 July 2017.
  6. ↑ 6.0 6.1 "Asteroid (617) Patroclus – Proper elements". AstDyS-2, Asteroids – Dynamic Site. Retrieved 13 June 2018.
  7. ↑ Template:Dict.com
  8. ↑ Riggs (1972) The Christian poet in Paradise lost
  9. ↑ Johnston, Wm. Robert (21 September 2014). "(617) Patroclus and Menoetius". johnstonsarchive.net. Retrieved 11 July 2017.
  10. ↑ 10.0 10.1 10.2 10.3 10.4 10.5 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. S2CID 121095409. Retrieved 11 July 2017.
  11. ↑ 11.0 11.1 11.2 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)
  12. ↑ 12.0 12.1 12.2 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)
  13. ↑ 13.0 13.1 13.2 Tedesco, E. F.; Noah, P. V.; Noah, M.; Price, S. D. (October 2004). "IRAS Minor Planet Survey V6.0". NASA Planetary Data System: IRAS-A-FPA-3-RDR-IMPS-V6.0. Bibcode:2004PDSS...12.....T. Retrieved 13 June 2018.
  14. ↑ 14.0 14.1 14.2 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.
  15. ↑ 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. 11 (12): 197–200. Bibcode:1991AdSpR..11..197G. doi:10.1016/0273-1177(91)90563-Y. ISSN 0273-1177. Retrieved 11 July 2017.
  16. ↑ 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. arXiv:astro-ph/0602033. Bibcode:2006Natur.439..565M. doi:10.1038/nature04350. PMID 16452974. S2CID 4416425. Retrieved 11 July 2017.
  17. ↑ Behrend, Raoul. "Asteroids and comets rotation curves – (617) Patroclus". Geneva Observatory. Retrieved 11 July 2017.
  18. ↑ 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:0908.4198. Bibcode:2010Icar..205..505M. doi:10.1016/j.icarus.2009.07.043. S2CID 118634843.
  19. ↑ 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.
  20. ↑ 20.0 20.1 20.2 20.3 "Asteroid 617 Patroclus". Small Bodies Data Ferret. Retrieved 13 June 2018.
  21. ↑ 21.0 21.1 21.2 Chatelain, Joseph P.; Henry, Todd J.; French, Linda M.; Winters, Jennifer G.; Trilling, David E. (June 2016). "Photometric colors of the brightest members of the Jupiter L5 Trojan cloud". Icarus. 271: 158–169. Bibcode:2016Icar..271..158C. doi:10.1016/j.icarus.2016.01.026.

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