2241 Alcathous

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2241 Alcathous
Discovery [1]
Discovered by C. Kowal
Discovery site Palomar Obs.
Discovery date 22 November 1979
MPC designation 2241 Alcathous
Named after
(Greek mythology, Iliad)[2]
1979 WM · 1950 NC
1968 WF
Jupiter trojan[3]
Orbital characteristics[1]
Epoch 13 January 2016 (JD 2457400.5)
Uncertainty parameter 0
Observation arc 65.75 yr (24016 days)
Aphelion 5.5346 AU (827.96 Gm)
Perihelion 4.8397 AU (724.01 Gm)
5.1871 AU (775.98 Gm)
Eccentricity 0.066984
11.81 yr (4315.05 d)
0° 5m 0.344s / day
Inclination 16.619°
Earth MOID 3.87735 AU (580.043 Gm)
Jupiter MOID 0.149076 AU (22.3015 Gm)
Jupiter Tisserand parameter 2.912
Physical characteristics
Dimensions 114.63 km[4]
118.87±2.27 km[5]
113.68±1.72 km[6]
Mean radius
57.315 ± 2.9 km
7.689 h (0.3204 d)[7]
9.41 h[8]
7.687±0.005 h[9]
7.690±0.001 h[10]
7.695±0.002 h[11]
7.691±0.001 h[a]
B–V = 0.728
U–B = 0.226
Tholen = D[1]

2241 Alcathous, provisional designation 1979 WM, is a large, dark and reddish Jupiter trojan, about 114 kilometers in diameter. It was discovered on 22 November 1979, by American astronomer Charles Kowal at the U.S. Palomar Observatory in southern California.[12]

It is classified as a D-type asteroid in the Tholen taxonomic classification, and the eighth largest of a total of 46 known asteroids of this spectral type.[13] It orbits the Sun at a distance of 4.8–5.5 AU once every 11 years and 10 months (4,317 days). Its orbit is tilted by 17 degrees to the plane of the ecliptic and shows an eccentricity of 0.07. The body has a well-determined rotation period of 7.69 hours, measured by several concurring photometric light-curve observations with a brightness variation of 0.20–0.25 magnitude, published during 2011–2015,[7][9][10][11][a] superseding a less accurate analysis from the 1990s.[8]

Based on the surveys carried out by the Infrared Astronomical Satellite, IRAS, the Japanese Akari satellite, and on preliminary results from the Wide-field Infrared Survey Explorer's NEOWISE mission, the asteroid has a low geometric albedo in the range of 0.04 to 0.05, a typical value for its spectral type.[4][5][6]

It is named after Alcathous, brave and handsome Trojan leader in Homer's Iliad. Alcathous was the husband of Hippodamia (also see 692 Hippodamia) the eldest daughter of Anchises (also see 1173 Anchises), who excelled all other girls of her age in beauty, skill and wit. Alcathous, previously uninjured in the Trojan War, was struck by Poseidon (also see 4341 Poseidon) with blindness and paralysis and was killed easily by a spear thrown by the Greek general and Cretan commander, Idomeneus (also see 2759 Idomeneus).[2]


  1. ^ a b Coley (2015) web: rotation period 7.691±0.001 hours with a brightness amplitude of 0.24 mag. Summary figures at Collaborative Asteroid Lightcurve Link (CALL) for (2241) Alcathous
  1. ^ a b c d "JPL Small-Body Database Browser: 2241 Alcathous (1979 WM)" (2015-11-21 last obs.). Jet Propulsion Laboratory. Retrieved 15 April 2016. 
  2. ^ a b Schmadel, Lutz D. (2003). Dictionary of Minor Planet Names – (2241) Alcathous. Springer Berlin Heidelberg. p. 182. ISBN 978-3-540-29925-7. Retrieved December 2015. 
  3. ^ a b "LCDB Data for (2241) Alcathous". Asteroid Lightcurve Database (LCDB). Retrieved December 2015. 
  4. ^ a b c 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 December 2015. 
  5. ^ a b c 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 December 2015. 
  6. ^ a b c Mainzer, A.; Grav, T.; Masiero, J.; Hand, E.; Bauer, J.; Tholen, D.; et al. (November 2011). "NEOWISE Studies of Spectrophotometrically Classified Asteroids: Preliminary Results". The Astrophysical Journal 741 (2): 25. arXiv:1109.6407. Bibcode:2011ApJ...741...90M. doi:10.1088/0004-637X/741/2/90. Retrieved December 2015. 
  7. ^ a b Stephens, Robert D.; Coley, Daniel R.; French, Linda M. (July 2015). "Dispatches from the Trojan Camp - Jovian Trojan L5 Asteroids Observed from CS3: 2014 October - 2015 January". The Minor Planet Bulletin 42 (3): 216–224. Bibcode:2015MPBu...42R.216S. ISSN 1052-8091. Retrieved December 2015. 
  8. ^ a b de Sanctis, M. C.; Barucci, M. A.; Angeli, C. A.; Fulchignoni, M.; Burchi, R.; Angelini, P. (October 1994). "Photoelectric and CCD observations of 10 asteroids". Planetary and Space Science: 859–864. Bibcode:1994P&SS...42..859D. doi:10.1016/0032-0633(94)90066-3. ISSN 0032-0633. Retrieved December 2015. 
  9. ^ a b 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. Retrieved December 2015. 
  10. ^ a b French, Linda M.; Stephens, Robert D.; Lederer, Susan M.; Coley, Daniel R.; Rohl, Derrick A. (April 2011). "Preliminary Results from a Study of Trojan Asteroids". The Minor Planet Bulletin 38 (2): 116–120. Bibcode:2011MPBu...38..116F. ISSN 1052-8091. Retrieved December 2015. 
  11. ^ a b Stephens, Robert D.; French, Linda M.; Davitt, Chelsea; Coley, Daniel R. (April 2014). "At the Scaean Gates: Observations Jovian Trojan Asteroids, July- December 2013". The Minor Planet Bulletin 41 (2): 95–100. Bibcode:2014MPBu...41...95S. ISSN 1052-8091. Retrieved December 2015. 
  12. ^ "2241 Alcathous (1979 WM)". Minor Planet Center. Retrieved December 2015. 
  13. ^ "JPL Small-Body Database Search list of D-type minor planets (Tholen and SMASSII)". JPL Solar System Dynamics. Retrieved December 2015. 

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