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
Pronunciation ælˈkæθoʊəs (al-kath'-oe-əs)
Named after
(Greek mythology, Iliad)[2]
1979 WM · 1950 NC
1968 WF
Jupiter trojan[3]
(Trojan camp)[4]
Orbital characteristics[1]
Epoch 16 February 2017 (JD 2457800.5)
Uncertainty parameter 0
Observation arc 66.38 yr (24,246 days)
Aphelion 5.5335 AU
Perihelion 4.8356 AU
5.1846 AU
Eccentricity 0.0673
11.81 yr (4,312 days)
Inclination 16.624°
Jupiter MOID 0.1467 AU
Jupiter Tisserand parameter 2.9120
Physical characteristics
Dimensions 113.68±1.72 km[5]
114.63 km[7]
118.87±2.27 km[8]
7.689±0.001 h[9]
7.687±0.005 h[10]
7.690±0.001 h[11]
7.691±0.001 h[12]
7.695±0.002 h[13]
9.41 h (dated)[14]
B–V = 0.728[1]
U–B = 0.226[1]
Tholen = D[1] · D[3]
8.61±0.25[15] · 8.64[1][3][5][7][8]

2241 Alcathous (AL-kath'-OE-əs), provisional designation 1979 WM, is a dark and reddish Jupiter trojan, approximately 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.[16] It is named after Alcathous from Greek mythology.[2]


Alcathous orbits the Sun at a distance of 4.8–5.5 AU once every 11 years and 10 months (4,312 days). Its orbit has an eccentricity of 0.07 and an inclination of 17° with respect to the ecliptic.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.[1]

A first precovery was taken at Palomar Observatory in June 1950, extending the body's observation arc by 29 years prior to its official discovery observation.[16]

Physical characteristics[edit]

Alcathous 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.[17]

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, Alcathous has a low geometric albedo in the range of 0.04 to 0.05, a typical value for its spectral type.[5][7][8]

Alcathous has a well-determined rotation period of 7.69 hours, measured by several concurring photometric lightcurve observations with a brightness variation of 0.20–0.25 magnitude, published during 2011–2015,[9][10][11][12][13] and superseding a less accurate analysis from the 1990s.[14]


This minor planet was 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] Naming citation was published on 10 November 1992 (M.P.C. 21128).[18]


  1. ^ a b c d e f g "JPL Small-Body Database Browser: 2241 Alcathous (1979 WM)" (2016-11-05 last obs.). Jet Propulsion Laboratory. Retrieved 7 December 2016. 
  2. ^ a b c Schmadel, Lutz D. (2007). Dictionary of Minor Planet Names – (2241) Alcathous. Springer Berlin Heidelberg. p. 182. ISBN 978-3-540-00238-3. Retrieved 7 December 2016. 
  3. ^ a b c "LCDB Data for (2241) Alcathous". Asteroid Lightcurve Database (LCDB). Retrieved 7 December 2016. 
  4. ^ "List of Jupiter Trojans". Minor Planet Center. 20 June 2016. Retrieved 7 December 2016. 
  5. ^ a b c d 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. arXiv:1109.6407Freely accessible. Bibcode:2011ApJ...741...90M. doi:10.1088/0004-637X/741/2/90. Retrieved 7 December 2016. 
  6. ^ a b 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:1209.1549Freely accessible. Bibcode:2012ApJ...759...49G. doi:10.1088/0004-637X/759/1/49. Retrieved 7 December 2016. 
  7. ^ 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. Bibcode:2004PDSS...12.....T. Retrieved 7 December 2016. 
  8. ^ 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" (PDF). Publications of the Astronomical Society of Japan. 63 (5): 1117–1138. Bibcode:2011PASJ...63.1117U. doi:10.1093/pasj/63.5.1117. Retrieved 7 December 2016. 
  9. ^ 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 7 December 2016. 
  10. ^ 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 7 December 2016. 
  11. ^ 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 7 December 2016. 
  12. ^ a b Stephens, Robert D.; Coley, Daniel R.; Warner, Brian D.; French, Linda, M. (October 2016). "Lightcurves of Jovian Trojan Asteroids from the Center for Solar System Studies: L4 Greek Camp and Spies". The Minor Planet Bulletin. 43 (4): 323–331. Bibcode:2016MPBu...43..323S. ISSN 1052-8091. Retrieved 7 December 2016. 
  13. ^ 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 7 December 2016. 
  14. ^ 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 7 December 2016. 
  15. ^ 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:1506.00762Freely accessible. Bibcode:2015Icar..261...34V. doi:10.1016/j.icarus.2015.08.007. Retrieved 7 December 2016. 
  16. ^ a b "2241 Alcathous (1979 WM)". Minor Planet Center. Retrieved 7 December 2016. 
  17. ^ "JPL Small-Body Database Search list of D-type minor planets (Tholen and SMASSII)". JPL Solar System Dynamics. Retrieved 15 December 2015. 
  18. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 7 December 2016. 

External links[edit]