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1208 Troilus

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1208 Troilus
Hubble Space Telescope image of Troilus taken in 2012
Discovery[1]
Discovered byK. Reinmuth
Discovery siteHeidelberg Obs.
Discovery date31 December 1931
Designations
(1208) Troilus
Pronunciation/ˈtroʊɪləs, ˈtrɔɪləs/[2][3]
Named after
Troilus (Greek mythology)[4]
1931 YA · 1965 WK
Jupiter trojan[1][5][6]
Trojan[7][8] · background[8]
AdjectivesTroilian
Orbital characteristics[5]
Epoch 23 March 2018 (JD 2458200.5)
Uncertainty parameter 0
Observation arc86.40 yr (31,557 d)
Aphelion5.7305 AU
Perihelion4.7712 AU
5.2509 AU
Eccentricity0.0913
12.03 yr (4,395 d)
189.17°
0° 4m 54.84s / day
Inclination33.542°
48.546°
296.06°
Jupiter MOID0.001 AU
TJupiter2.6590
Physical characteristics
100.48±1.10 km[9]
103.31 km (derived)[6]
103.34±3.9 km[10]
111.36±2.36 km[11]
24 h[12]
56.17±0.07 h[13]
63.8±0.5 h[14]
0.037±0.002[11]
0.0397 (derived)[6]
0.041±0.006[9]
0.0419±0.003[10]
FCU (Tholen)[5][6]
C0 (Barucci)
U–B = 0.314±093[5]
B–V = 0.750±0.050[15]
V–R = 0.380±0.030[15]
V–I = 0.740±0.020[6]
8.99[1][5][10][11]
9.05[6][12]
9.08[9][16]

1208 Troilus /ˈtroʊɪləs/ is a large and notably inclined Jupiter trojan from the Trojan camp, approximately 103 kilometers (64 miles) in diameter. It was discovered on 31 December 1931, by German astronomer Karl Reinmuth at the Heidelberg Observatory in southern Germany.[1] The unusual F-type asteroid belongs to the largest Jupiter trojans and has a long rotation period of 56.2 hours.[6] It was named after the Trojan prince Troilus, who was killed by Achilles.[4]

Orbit and classification

Troilus is a dark Jovian asteroid orbiting in the trailing Trojan camp at Jupiter's L5 Lagrangian point, 60° behind its orbit in a 1:1 resonance (see Trojans in astronomy). It is also a non-family asteroid of the Jovian background population.[8][17]

It orbits the Sun at a distance of 4.8–5.7 AU once every 12 years (4,395 days; semi-major axis of 5.25 AU). Its orbit has an eccentricity of 0.09 and a high inclination of 34° with respect to the ecliptic.[5] The body's observation arc begins with its official discovery observation at Heidelberg in December 1931.[1]

Physical characteristics

In the Tholen classification, Troilus has an ambiguous and unusual spectrum, closest to that of an F-type and somewhat similar to a common C-type asteroid (FCU).[5][6] It has also been characterized as a carbonaceous C-type in the Barucci taxonomy (C0-type).[17]

Rotation period

In April 2007, a rotational lightcurve of Troilus was obtained from photometric observations by Lawrence Molnar at the Calvin-Rehoboth Robotic Observatory (G98) in New Mexico. Lightcurve analysis gave a rotation period of 56.17±0.07 hours with a brightness variation of 0.20±0.02 magnitude (U=2).[6][13] While not being a slow rotator, Troilus has a significantly longer period than most asteroids, and one of longest of all larger Jupiter trojans.

The period also supersedes previous observations made by Linda French with the 0.9-meter SMARTS telescope at Cerro Tololo in the 1980s and by Federico Manzini at the Sozzago Astronomical Station (A12), which gave a period of 24 and 63.8 hours, respectively (U=2/1).[12][14]

Diameter and albedo

According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the Japanese Akari satellite and the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Troilus measures between 100.48 and 111.36 kilometers in diameter and its surface has an albedo between 0.037 and 0.0419.[9][10][11] The Collaborative Asteroid Lightcurve Link derives an albedo of 0.0397 and a diameter of 103.31 kilometers based on an absolute magnitude of 9.05.[6]

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 Hektor 7.2 225 233 230.99 L4 6.92 0.930 1907 list
617 Patroclus 8.19 140.362 140.92 140.85 L5 102.80 0.830 1906 list
911 Agamemnon 7.89 131.038 166.66 185.30 L4 6.59 0.980 1919 list
588 Achilles 8.67 130.099 135.47 133.22 L4 7.31 0.940 1906 list
3451 Mentor 8.4 126.288 116.30 117.91 L5 7.70 0.770 1984 list
3317 Paris 8.3 118.790 116.26 120.45 L5 7.09 0.950 1984 list
1867 Deiphobus 8.3 118.220 122.67 131.31 L5 58.66 0.930 1971 list
1172 Äneas 8.33 118.020 142.82 148.66 L5 8.71 0.950 1930 list
1437 Diomedes 8.3 117.786 164.31 172.60 L4 24.49 0.810 1937 list
1143 Odysseus 7.93 114.624 125.64 130.81 L4 10.11 0.860 1930 list
2241 Alcathous 8.64 113.682 114.63 118.87 L5 7.69 0.940 1979 list
659 Nestor 8.99 112.320 108.87 107.06 L4 15.98 0.790 1908 list
3793 Leonteus 8.7 112.046 86.26 87.58 L4 5.62 0.780 1985 list
3063 Makhaon 8.4 111.655 116.14 114.34 L4 8.64 0.830 1983 list
1583 Antilochus 8.6 108.842 101.62 111.69 L4 31.54 0.950 1950 list
884 Priamus 8.81 101.093 96.29 119.99 L5 6.86 0.900 1917 list
1208 Troilus 8.99 100.477 103.34 111.36 L5 56.17 0.740 1931 list
1173 Anchises 8.89 99.549 126.27 120.49 L5 11.60 0.780 1930 list
2207 Antenor 8.89 97.658 85.11 91.32 L5 7.97 0.950 1977 list
2363 Cebriones 9.11 95.976 81.84 84.61 L5 20.05 0.910 1977 list
4063 Euforbo 8.7 95.619 102.46 106.38 L4 8.85 0.950 1989 list
2357 Phereclos 8.94 94.625 94.90 98.45 L5 14.39 0.960 1981 list
4709 Ennomos 8.5 91.433 80.85 80.03 L5 12.28 0.690 1988 list
2797 Teucer 8.7 89.430 111.14 113.99 L4 10.15 0.920 1981 list
2920 Automedon 8.8 88.574 111.01 113.11 L4 10.21 0.950 1981 list
15436 Dexius 9.1 87.646 85.71 78.63 L4 8.97 0.870 1998 list
3596 Meriones 9.2 87.380 75.09 73.28 L4 12.96 0.830 1985 list
2893 Peiroos 9.23 86.884 87.46 86.76 L5 8.96 0.950 1975 list
4086 Podalirius 9.1 85.495 86.89 85.98 L4 10.43 0.870 1985 list
4060 Deipylos 9.3 84.043 79.21 86.79 L4 9.30 0.760 1987 list
1404 Ajax 9.3 83.990 81.69 96.34 L4 29.38 0.960 1936 list
4348 Poulydamas 9.5 82.032 70.08 87.51 L5 9.91 0.840 1988 list
5144 Achates 9.0 80.958 91.91 89.85 L5 5.96 0.920 1991 list
4833 Meges 8.9 80.165 87.33 89.39 L4 14.25 0.940 1989 list
2223 Sarpedon 9.41 77.480 94.63 108.21 L5 22.74 0.880 1977 list
4489 Dracius 9.0 76.595 92.93 95.02 L4 12.58 0.950 1988 list
2260 Neoptolemus 9.31 76.435 71.65 81.28 L4 8.18 0.950 1975 list
5254 Ulysses 9.2 76.147 78.34 80.00 L4 28.72 0.970 1986 list
3708 Socus 9.3 75.661 79.59 76.75 L5 6.55 0.980 1974 list
2674 Pandarus 9.1 74.267 98.10 101.72 L5 8.48 1.000 1982 list
3564 Talthybius 9.4 73.730 68.92 74.11 L4 40.59 0.900 1985 list
4834 Thoas 9.1 72.331 86.82 96.21 L4 18.19 0.950 1989 list
7641 Cteatus 9.4 71.839 68.97 75.28 L4 27.77 0.980 1986 list
3540 Protesilaos 9.3 70.225 76.84 87.66 L4 8.95 0.940 1973 list
11395 Iphinous 9.8 68.977 64.71 67.78 L4 17.38 – 1998 list
4035 Thestor 9.6 68.733 68.23 66.99 L4 13.47 0.970 1986 list
5264 Telephus 9.4 68.472 73.26 81.38 L4 9.53 0.970 1991 list
1868 Thersites 9.5 68.163 70.08 78.89 L4 10.48 0.960 1960 list
9799 Thronium 9.6 68.033 64.87 72.42 L4 21.52 0.910 1996 list
4068 Menestheus 9.5 67.625 62.37 68.46 L4 14.40 0.950 1973 list
23135 Pheidas 9.9 66.230 58.29 68.50 L4 8.69 0.860 2000 list
2456 Palamedes 9.3 65.916 91.66 99.60 L4 7.24 0.920 1966 list
3709 Polypoites 9.1 65.297 99.09 85.23 L4 10.04 1.000 1985 list
1749 Telamon 9.5 64.898 81.06 69.14 L4 16.98 0.970 1949 list
3548 Eurybates 9.6 63.885 72.14 68.40 L4 8.71 0.730 1973 list
4543 Phoinix 9.7 63.836 62.79 69.54 L4 38.87 1.200 1989 list
12444 Prothoon 9.8 63.835 64.31 62.41 L5 15.82 – 1996 list
4836 Medon 9.5 63.277 67.73 78.70 L4 9.82 0.920 1989 list
16070 Charops 9.7 63.191 64.13 68.98 L5 20.24 0.960 1999 list
15440 Eioneus 9.6 62.519 66.48 71.88 L4 21.43 0.970 1998 list
4715 Medesicaste 9.7 62.097 63.91 65.93 L5 8.81 0.850 1989 list
34746 Thoon 9.8 61.684 60.51 63.63 L5 19.63 0.950 2001 list
38050 Bias 9.8 61.603 61.04 50.44 L4 18.85 0.990 1998 list
5130 Ilioneus 9.7 60.711 59.40 52.49 L5 14.77 0.960 1989 list
5027 Androgeos 9.6 59.786 57.86 n.a. L4 11.38 0.910 1988 list
6090 Aulis 9.4 59.568 74.53 81.92 L4 18.48 0.980 1989 list
5648 Axius 9.7 59.295 63.91 n.a. L5 37.56 0.900 1990 list
7119 Hiera 9.7 59.150 76.40 77.29 L4 400 0.950 1989 list
4805 Asteropaios 10.0 57.647 53.16 43.44 L5 12.37 – 1990 list
16974 Iphthime 9.8 57.341 55.43 57.15 L4 78.9 0.960 1998 list
4867 Polites 9.8 57.251 58.29 64.29 L5 11.24 1.010 1989 list
2895 Memnon 10.0 56.706 55.67 n.a. L5 7.50 0.710 1981 list
4708 Polydoros 9.9 54.964 55.67 n.a. L5 7.52 0.960 1988 list
(21601) 1998 XO89 10.0 54.909 55.67 56.08 L4 12.65 0.970 1998 list
12929 Periboea 9.9 54.077 61.04 55.34 L5 9.27 0.880 1999 list
17492 Hippasos 10.0 53.975 55.67 n.a. L5 17.75 – 1991 list
5652 Amphimachus 10.1 53.921 53.16 52.48 L4 8.37 1.050 1992 list
2759 Idomeneus 9.9 53.676 61.01 52.55 L4 32.38 0.910 1980 list
5258 Rhoeo 10.2 53.275 50.77 n.a. L4 19.85 1.010 1989 list
(12126) 1999 RM11 10.1 53.202 n.a. n.a. L5 n.a. ? 1999 list
(15502) 1999 NV27 10.0 53.100 55.67 50.86 L5 15.13 0.875 1999 list
4754 Panthoos 10.0 53.025 53.15 56.96 L5 27.68 – 1977 list
4832 Palinurus 10.0 52.058 53.16 n.a. L5 5.32 1.000 1988 list
5126 Achaemenides 10.5 51.922 44.22 48.57 L4 53.02 – 1989 list
3240 Laocoon 10.2 51.695 50.77 n.a. L5 11.31 0.880 1978 list
4902 Thessandrus 9.8 51.263 61.04 71.79 L4 738 0.960 1989 list
11552 Boucolion 10.1 51.136 53.16 53.91 L5 32.44 – 1993 list
(20729) 1999 XS143 10.4 50.961 46.30 n.a. L4 5.72 1.000 1999 list
6545 Leitus 10.1 50.951 53.16 n.a. L4 16.26 0.910 1986 list
4792 Lykaon 10.1 50.870 53.16 n.a. L5 40.09 0.960 1988 list
21900 Orus 10.0 50.810 55.67 53.87 L4 13.45 0.950 1999 list
1873 Agenor 10.1 50.799 53.76 54.38 L5 20.60 – 1971 list
5028 Halaesus 10.2 50.770 50.77 n.a. L4 24.94 0.900 1988 list
2146 Stentor 9.9 50.755 58.29 n.a. L4 16.40 – 1976 list
4722 Agelaos 10.0 50.378 53.16 59.47 L5 18.44 0.910 1977 list
5284 Orsilocus 10.1 50.159 53.16 n.a. L4 10.31 0.970 1989 list
11509 Thersilochos 10.1 49.960 53.16 56.23 L5 17.37 – 1990 list
5285 Krethon 10.1 49.606 58.53 52.61 L4 12.04 1.090 1989 list
4791 Iphidamas 10.1 49.528 57.85 59.96 L5 9.70 1.030 1988 list
9023 Mnesthus 10.1 49.151 50.77 60.80 L5 30.66 – 1988 list
5283 Pyrrhus 9.7 48.356 64.58 69.93 L4 7.32 0.950 1989 list
4946 Askalaphus 10.2 48.209 52.71 66.10 L4 22.73 0.940 1988 list
(22149) 2000 WD49 10.2 48.190 50.77 50.37 L4 7.84 1.090 2000 list
(32496) 2000 WX182 10.2 48.017 50.77 51.63 L5 23.34 0.950 2000 list
5120 Bitias 10.2 47.987 50.77 n.a. L5 15.21 0.780 1988 list
12714 Alkimos 10.1 47.819 61.04 54.62 L4 28.48 – 1991 list
7352 Hypsenor 9.9 47.731 55.67 47.07 L5 648 0.850 1994 list
1870 Glaukos 10.6 47.649 42.23 n.a. L5 5.99 — 1971 list
4138 Kalchas 10.1 46.462 53.16 61.04 L4 29.2 0.810 1973 list
(23958) 1998 VD30 10.2 46.001 50.77 47.91 L4 562 0.990 1998 list
4828 Misenus 10.4 45.954 46.30 43.22 L5 12.87 0.920 1988 list
4057 Demophon 10.1 45.683 53.16 n.a. L4 29.82 1.060 1985 list
4501 Eurypylos 10.4 45.524 46.30 n.a. L4 6.05 – 1989 list
4007 Euryalos 10.3 45.515 48.48 53.89 L4 6.39 – 1973 list
5259 Epeigeus 10.3 44.741 42.59 44.42 L4 18.42 – 1989 list
30705 Idaios 10.4 44.546 46.30 n.a. L5 15.74 – 1977 list
16560 Daitor 10.7 43.861 51.42 43.38 L5 – – 1991 list
(15977) 1998 MA11 10.4 43.530 46.30 51.53 L5 250 0.906 1998 list
7543 Prylis 10.6 42.893 42.23 n.a. L4 17.80 – 1973 list
4827 Dares 10.5 42.770 44.22 n.a. L5 19.00 – 1988 list
1647 Menelaus 10.5 42.716 44.22 n.a. L4 17.74 0.866 1957 list
(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 from Greek mythology after the young Trojan prince Troilus, the son of King Priam (also see 884 Priamus), who in a medieval legend loved Cressida (see 548 Kressida) and lost her to Diomedes (see 1437 Diomedes). Troilus was killed by Achilles (see 588 Achilles) in the Trojan War. The official naming citation was published by Paul Herget in The Names of the Minor Planets in 1955 (H 112).[4]

References

  1. ^ a b c d e "1208 Troilus (1931 YA)". Minor Planet Center. Retrieved 12 June 2018.
  2. ^ Noah Webster (1884) A Practical Dictionary of the English Language
  3. ^ "Troilus". Dictionary.com Unabridged (Online). n.d.
  4. ^ a b c Schmadel, Lutz D. (2007). "(1208) Troilus". Dictionary of Minor Planet Names. Springer Berlin Heidelberg. p. 101. doi:10.1007/978-3-540-29925-7_1209. ISBN 978-3-540-00238-3.
  5. ^ a b c d e f g "JPL Small-Body Database Browser: 1208 Troilus (1931 YA)" (2018-05-25 last obs.). Jet Propulsion Laboratory. Retrieved 12 June 2018.
  6. ^ a b c d e f g h i j "LCDB Data for (1208) Troilus". Asteroid Lightcurve Database (LCDB). Retrieved 12 June 2018.
  7. ^ "List of Jupiter Trojans". Minor Planet Center. 30 May 2018. Retrieved 6 June 2018.
  8. ^ a b c "Asteroid (1208) Troilus – Proper elements". AstDyS-2, Asteroids – Dynamic Site. Retrieved 12 June 2018.
  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 d 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.
  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. ^ a b c French, L. M. (November 1987). "Rotation properties of four L5 Trojan asteroids from CCD photometry". Icarus. 72 (2): 325–341.MIT–supportedresearch. Bibcode:1987Icar...72..325F. doi:10.1016/0019-1035(87)90178-3. ISSN 0019-1035. Retrieved 22 November 2015.
  13. ^ a b 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. Retrieved 22 November 2015.
  14. ^ a b Behrend, Raoul. "Asteroids and comets rotation curves – (1208) Troilus". Geneva Observatory. Retrieved 3 August 2017.
  15. ^ a b 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.
  16. ^ Schaefer, Martha W.; Schaefer, Bradley E.; Rabinowitz, David L.; Tourtellotte, Suzanne W. (June 2010). "Phase curves of nine Trojan asteroids over a wide range of phase angles". Icarus. 207 (2): 699–713. arXiv:0912.1888. Bibcode:2010Icar..207..699S. doi:10.1016/j.icarus.2009.11.031. S2CID 118589399.
  17. ^ a b "Asteroid 1208 Troilus". Small Bodies Data Ferret. Retrieved 12 June 2018.

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