2920 Automedon

2920 Automedon /ɔːˈtɒmɪdɒn/ is a large Jupiter trojan from the Greek camp, approximately 110 kilometers (68 miles) in diameter. It was discovered by American astronomer Edward Bowell at the Anderson Mesa station of the Lowell Observatory on 3 May 1981.[1] The dark D-type asteroid has a rotation period of 10.22 hours and belongs to the 30 largest Jupiter trojans.[4] It was named after the ancient Greek hero Automedon, the charioteer of Achilles.[1]

2920 Automedon
Discovery[1]
Discovered byE. Bowell
Discovery siteAnderson Mesa Stn.
Discovery date3 May 1981
Designations
(2920) Automedon
Pronunciation/ɔːˈtɒmɪdɒn/[2]
Named after
Automedon[1]
(Greek mythology)
1981 JR
Jupiter trojan[1][3][4]
Greek[5][6] · background[6]
Orbital characteristics[3]
Epoch 23 March 2018 (JD 2458200.5)
Uncertainty parameter 0
Observation arc36.97 yr (13,502 d)
Aphelion5.2417 AU
Perihelion4.9742 AU
5.1079 AU
Eccentricity0.0262
11.54 yr (4,217 d)
221.03°
0° 5m 7.44s / day
Inclination21.121°
230.94°
197.70°
Jupiter MOID0.0311 AU
TJupiter2.8670
Physical characteristics
Mean diameter
88.57±1.80 km[7]
111.01±7.5 km[8]
113.11±2.25 km[9]
10.212±0.002 h[10]
10.220±0.004 h[11]
10.223±0.003 h[12][lower-alpha 1]
0.042±0.002[9]
0.0433±0.007[8]
0.068±0.009[7]
D (SMASS-1)[13]
C (assumed)[4]
V–I = 0.950±0.015[4]
8.59±0.21[14]
8.80[3][7][8][9]

    Orbit and classification

    Automedon is a dark Jovian asteroid orbiting in the leading Greek camp at Jupiter's L4 Lagrangian point, 60° ahead of its orbit in a 1:1 resonance (see Trojans in astronomy). It is a non-family asteroid in the Jovian background population.[6][13]

    It orbits the Sun at a distance of 5.0–5.2 AU once every 11 years and 6 months (4,217 days; semi-major axis of 5.11 AU). Its orbit has an eccentricity of 0.03 and an inclination of 21° with respect to the ecliptic.[3] The body's observation arc begins with its official discovery observation at Anderson Mesa.[1]

    Physical characteristics

    In the SMASS classification, Automedon is a dark D-type asteroid (first SMASS survey, Xu 1995).[13] It is also a generically assumed C-type asteroid.[4]

    Rotation period

    Three rotational lightcurves of Automedon have been obtained from photometric observations, that are all in good agreement.[4]

    In June 1994, observations by Stefano Mottola using the now decommissioned Bochum 0.61-metre Telescope at ESO's La Silla Observatory in Chile gave a rotation period of 10.220 hours with a brightness variation of 0.12 magnitude (U=3).[11]

    A second lightcurve gave a period of 10.212 hours with an amplitude of 0.17 magnitude. It was measured in July 2007, by astronomers using telescopes at the Calvin College Observatory (H62) in Michigan and the Calvin-Rehoboth Robotic Observatory in New Mexico (U=3).[10] In June 2017, another observation by Brian Warner and Robert Stephens at the Center for Solar System Studies (U81) in California gave a period of 10.223 hours with an amplitude of 0.11 magnitude (U=3-).[12][lower-alpha 1]

    Diameter and albedo

    According to the surveys carried out by the Japanese Akari satellite, the Infrared Astronomical Satellite IRAS, and the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Automedon measures between 88.57 and 113.11 kilometers in diameter and its surface has an albedo between 0.042 and 0.068.[7][8][9]

    The Collaborative Asteroid Lightcurve Link adopts the results obtained by IRAS, that is, an albedo of 0.0433 and a diameter of 111.01 kilometers based on an absolute magnitude of 8.8.[4]

    100+ largest Jupiter trojans
    Largest Jupiter Trojans by survey(A)
    (mean-diameter in kilometers; YoD: Year of Discovery)
    Designation H WISE IRAS Akari Ln RP V–I YoD Ref
    624 Hektor7.2225233230.99L46.920.9301907list
    617 Patroclus8.19140.362140.92140.85L5102.800.8301906list
    911 Agamemnon7.89131.038166.66185.30L46.590.9801919list
    588 Achilles8.67130.099135.47133.22L47.310.9401906list
    3451 Mentor8.4126.288116.30117.91L57.700.7701984list
    3317 Paris8.3118.790116.26120.45L57.090.9501984list
    1867 Deiphobus8.3118.220122.67131.31L558.660.9301971list
    1172 Äneas8.33118.020142.82148.66L58.710.9501930list
    1437 Diomedes8.3117.786164.31172.60L424.490.8101937list
    1143 Odysseus7.93114.624125.64130.81L410.110.8601930list
    2241 Alcathous8.64113.682114.63118.87L57.690.9401979list
    659 Nestor8.99112.320108.87107.06L415.980.7901908list
    3793 Leonteus8.7112.04686.2687.58L45.620.7801985list
    3063 Makhaon8.4111.655116.14114.34L48.640.8301983list
    1583 Antilochus8.6108.842101.62111.69L431.540.9501950list
    884 Priamus8.81101.09396.29119.99L56.860.9001917list
    1208 Troilus8.99100.477103.34111.36L556.170.7401931list
    1173 Anchises8.8999.549126.27120.49L511.600.7801930list
    2207 Antenor8.8997.65885.1191.32L57.970.9501977list
    2363 Cebriones9.1195.97681.8484.61L520.050.9101977list
    4063 Euforbo8.795.619102.46106.38L48.850.9501989list
    2357 Phereclos8.9494.62594.9098.45L514.390.9601981list
    4709 Ennomos8.591.43380.8580.03L512.280.6901988list
    2797 Teucer8.789.430111.14113.99L410.150.9201981list
    2920 Automedon8.888.574111.01113.11L410.210.9501981list
    (15436) 1998 VU309.187.64685.7178.63L48.970.8701998list
    3596 Meriones9.287.38075.0973.28L412.960.8301985list
    2893 Peiroos9.2386.88487.4686.76L58.960.9501975list
    4086 Podalirius9.185.49586.8985.98L410.430.8701985list
    4060 Deipylos9.384.04379.2186.79L49.300.7601987list
    1404 Ajax9.383.99081.6996.34L429.380.9601936list
    4348 Poulydamas9.582.03270.0887.51L59.910.8401988list
    5144 Achates9.080.95891.9189.85L55.960.9201991list
    4833 Meges8.980.16587.3389.39L414.250.9401989list
    2223 Sarpedon9.4177.48094.63108.21L522.740.8801977list
    (4489) 1988 AK9.076.59592.9395.02L412.580.9501988list
    2260 Neoptolemus9.3176.43571.6581.28L48.180.9501975list
    5254 Ulysses9.276.14778.3480.00L428.720.9701986list
    (3708) 1974 FV19.375.66179.5976.75L56.550.9801974list
    2674 Pandarus9.174.26798.10101.72L58.481.0001982list
    3564 Talthybius9.473.73068.9274.11L440.590.9001985list
    4834 Thoas9.172.33186.8296.21L418.190.9501989list
    (7641) 1986 TT69.471.83968.9775.28L427.770.9801986list
    3540 Protesilaos9.370.22576.8487.66L48.950.9401973list
    (11395) 1998 XN779.868.97764.7167.78L417.381998list
    (4035) 1986 WD9.668.73368.2366.99L413.470.9701986list
    5264 Telephus9.468.47273.2681.38L49.530.9701991list
    1868 Thersites9.568.16370.0878.89L410.480.9601960list
    (9799) 1996 RJ9.668.03364.8772.42L421.520.9101996list
    4068 Menestheus9.567.62562.3768.46L414.400.9501973list
    (23135) 2000 AN1469.966.23058.2968.50L48.690.8602000list
    2456 Palamedes9.365.91691.6699.60L47.240.9201966list
    3709 Polypoites9.165.29799.0985.23L410.041.0001985list
    1749 Telamon9.564.89881.0669.14L416.980.9701949list
    3548 Eurybates9.663.88572.1468.40L48.710.7301973list
    4543 Phoinix9.763.83662.7969.54L438.871.2001989list
    12444 Prothoon9.863.83564.3162.41L515.821996list
    4836 Medon9.563.27767.7378.70L49.820.9201989list
    (16070) 1999 RB1019.763.19164.1368.98L520.240.9601999list
    (15440) 1998 WX49.662.51966.4871.88L421.430.9701998list
    (4715) 1989 TS19.762.09763.9165.93L58.810.8501989list
    (34746) 2001 QE919.861.68460.5163.63L519.630.9502001list
    (38050) 1998 VR389.861.60361.0450.44L418.850.9901998list
    5130 Ilioneus9.760.71159.4052.49L514.770.9601989list
    5027 Androgeos9.659.78657.86n.a.L411.380.9101988list
    (6090) 1989 DJ9.459.56874.5381.92L418.480.9801989list
    (5648) 1990 VU19.759.29563.91n.a.L537.560.9001990list
    7119 Hiera9.759.15076.4077.29L44000.9501989list
    4805 Asteropaios10.057.64753.1643.44L512.371990list
    16974 Iphthime9.857.34155.4357.15L478.90.9601998list
    4867 Polites9.857.25158.2964.29L511.241.0101989list
    2895 Memnon10.056.70655.67n.a.L57.500.7101981list
    4708 Polydoros9.954.96455.67n.a.L57.520.9601988list
    (21601) 1998 XO8910.054.90955.6756.08L412.650.9701998list
    (12929) 1999 TZ19.954.07761.0455.34L59.270.8801999list
    17492 Hippasos10.053.97555.67n.a.L517.751991list
    5652 Amphimachus10.153.92153.1652.48L48.371.0501992list
    2759 Idomeneus9.953.67661.0152.55L432.380.9101980list
    (5258) 1989 AU110.253.27550.77n.a.L419.851.0101989list
    (12126) 1999 RM1110.153.202n.a.n.a.L5n.a.?1999list
    (15502) 1999 NV2710.053.10055.6750.86L515.130.8751999list
    4754 Panthoos10.053.02553.1556.96L527.681977list
    4832 Palinurus10.052.05853.16n.a.L55.321.0001988list
    5126 Achaemenides10.551.92244.2248.57L453.021989list
    3240 Laocoon10.251.69550.77n.a.L511.310.8801978list
    4902 Thessandrus9.851.26361.0471.79L47380.9601989list
    11552 Boucolion10.151.13653.1653.91L532.441993list
    (20729) 1999 XS14310.450.96146.30n.a.L45.721.0001999list
    (6545) 1986 TR610.150.95153.16n.a.L416.260.9101986list
    4792 Lykaon10.150.87053.16n.a.L540.090.9601988list
    21900 Orus10.050.81055.6753.87L413.450.9501999list
    1873 Agenor10.150.79953.7654.38L520.601971list
    5028 Halaesus10.250.77050.77n.a.L424.940.9001988list
    2146 Stentor9.950.75558.29n.a.L416.401976list
    4722 Agelaos10.050.37853.1659.47L518.440.9101977list
    5284 Orsilocus10.150.15953.16n.a.L410.310.9701989list
    11509 Thersilochos10.149.96053.1656.23L517.371990list
    5285 Krethon10.149.60658.5352.61L412.041.0901989list
    4791 Iphidamas10.149.52857.8559.96L59.701.0301988list
    9023 Mnesthus10.149.15150.7760.80L530.661988list
    5283 Pyrrhus9.748.35664.5869.93L47.320.9501989list
    4946 Askalaphus10.248.20952.7166.10L422.730.9401988list
    (22149) 2000 WD4910.248.19050.7750.37L47.841.0902000list
    (32496) 2000 WX18210.248.01750.7751.63L523.340.9502000list
    5120 Bitias10.247.98750.77n.a.L515.210.7801988list
    12714 Alkimos10.147.81961.0454.62L428.481991list
    (7352) 1994 CO9.947.73155.67 47.07L56480.8501994list
    1870 Glaukos10.647.64942.23n.a.L55.991971list
    4138 Kalchas10.146.46253.1661.04L429.20.8101973list
    (23958) 1998 VD3010.246.00150.7747.91L45620.9901998list
    4828 Misenus10.445.95446.30 43.22L512.870.9201988list
    4057 Demophon10.145.68353.16n.a.L429.821.0601985list
    4501 Eurypylos10.445.52446.30n.a.L46.051989list
    4007 Euryalos10.345.51548.4853.89L46.391973list
    5259 Epeigeus10.344.74142.5944.42L418.421989list
    30705 Idaios10.444.54646.30n.a.L515.741977list
    16560 Daitor10.743.86151.4243.38L51991list
    (15977) 1998 MA1110.443.53046.3051.53L52500.9061998list
    7543 Prylis10.642.89342.23n.a.L417.801973list
    4827 Dares10.542.77044.22n.a.L519.001988list
    1647 Menelaus10.542.71644.22n.a.L417.740.8661957list
    (A) Used sources: WISE/NEOWISE catalog (NEOWISE_DIAM_V1 PDS, Grav, 2012); IRAS data (SIMPS v.6 catalog); and Akari catalog (Usui, 2011); RP: rotation period and V–I (color index) taken from the LCDB

    Note: missing data was completed with figures from the JPL SBDB (query) and from the LCDB (query form) for the WISE/NEOWISE and SIMPS catalogs, respectively. These figures are given in italics. Also, listing is incomplete above #100.

    Naming

    This minor planet was named after the Greek mythology hero Automedon, Greek mythology. He was the son of Diorês and the charioteer of Greek hero Achilles during the Trojan War. Automedon took revenge for the death of Patroclus by killing the Trojan Aretus.[1] The official naming citation was published by the Minor Planet Center on 17 February 1984 (M.P.C. 8544).[15]

    Notes

    1. Lightcurve plot of (2920) Automedon from June 2017 by Brian Warner and Robert Stephens at the Center for Solar System Studies (U81). Rotation period 10.223±0.003 hours with an amplitude of 0.11 mag. Quality code is 3-. Summary figures at the LCDB.

    References

    1. "2920 Automedon (1981 JR)". Minor Planet Center. Retrieved 30 May 2018.
    2. Noah Webster (1884) A Practical Dictionary of the English Language
    3. "JPL Small-Body Database Browser: 2920 Automedon (1981 JR)" (2018-04-21 last obs.). Jet Propulsion Laboratory. Retrieved 30 May 2018.
    4. "LCDB Data for (2920) Automedon". Asteroid Lightcurve Database (LCDB). Retrieved 30 May 2018.
    5. "List of Jupiter Trojans". Minor Planet Center. 2 February 2018. Retrieved 30 May 2018.
    6. "Asteroid (2920) Automedon". AstDyS-2, Asteroids – Dynamic Site. Retrieved 25 May 2018.
    7. 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. (online catalog)
    8. 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: IRAS-A-FPA-3-RDR-IMPS-V6.0. Bibcode:2004PDSS...12.....T. Retrieved 15 June 2018.
    9. 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 15 June 2018. (online, AcuA catalog p. 153)
    10. Molnar, Lawrence A.; Haegert, Melissa, J.; Hoogeboom, Kathleen M. (June 2008). "Lightcurve Analysis of an Unbiased Sample of Trojan Asteroids". The Minor Planet Bulletin. 35 (2): 82–84. Bibcode:2008MPBu...35...82M. ISSN 1052-8091.
    11. Mottola, Stefano; Di Martino, Mario; Erikson, Anders; Gonano-Beurer, Maria; Carbognani, Albino; Carsenty, Uri; et al. (May 2011). "Rotational Properties of Jupiter Trojans. I. Light Curves of 80 Objects". The Astronomical Journal. 141 (5): 32. Bibcode:2011AJ....141..170M. doi:10.1088/0004-6256/141/5/170.
    12. Stephens, Robert D.; Warner, Brian D. (October 2017). "Lightcurve Analysis of L4 Trojan Asteroids at the Center for Solar System Studies 2017 April-June". The Minor Planet Bulletin. 44 (4): 312–316. Bibcode:2017MPBu...44..312S. ISSN 1052-8091.
    13. "Asteroid 2920 Automedon". Small Bodies Data Ferret. Retrieved 30 May 2018.
    14. Veres, Peter; Jedicke, Robert; Fitzsimmons, Alan; Denneau, Larry; Granvik, Mikael; Bolin, Bryce; et al. (November 2015). "Absolute magnitudes and slope parameters for 250,000 asteroids observed by Pan-STARRS PS1 - Preliminary results". Icarus. 261: 34–47. arXiv:1506.00762. Bibcode:2015Icar..261...34V. doi:10.1016/j.icarus.2015.08.007.
    15. "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 30 May 2018.

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