4902 Thessandrus

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4902 Thessandrus
Discovery [1]
Discovered by C. Shoemaker
Discovery site Palomar Obs.
Discovery date 9 January 1989
MPC designation (4902) Thessandrus
Pronunciation the-san'-drəs
Named after
(Greek mythology)[2]
1989 AN2 · 1985 TK3
Jupiter trojan[3][4]
(Greek camp)[5]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc 63.27 yr (23,110 days)
Aphelion 5.4231 AU
Perihelion 4.9866 AU
5.2048 AU
Eccentricity 0.0419
11.87 yr (4,337 days)
0° 4m 58.8s / day
Inclination 9.0724°
Jupiter MOID 0.1990 AU
Jupiter Tisserand parameter 2.9730
Physical characteristics
Dimensions 51.263±0.664[6][7]
61.04 km (calculated)[4]
738±20 h[8]
0.057 (assumed)[4]
D[9] · C[4]
9.75±0.52[9] · 9.8[1][4][6]

4902 Thessandrus (the-san'-drəs), provisionally designated 1989 AN2, is a rare-type Jupiter trojan from the Greek camp and an exceptionally slow rotator, approximately 60 kilometers in diameter.

The Jovian asteroid was discovered on 9 January 1989, by American astronomer Carolyn Shoemaker at Palomar Observatory in California, United States.[3] It was named for Thessander (Thessandrus) from Greek mythology.[2]

Orbit and classification[edit]

Thessandrus orbits the Sun in the outer main-belt at a distance of 5.0–5.4 AU once every 11 years and 10 months (4,337 days). Its orbit has an eccentricity of 0.04 and an inclination of 9° with respect to the ecliptic.[1]

A first precovery was taken at the discovering observatory in 1954, extending the body's observation arc by 35 years prior to its official discovery observation.[3]

Physical characteristics[edit]

Thessandrus has been characterized as a D-type asteroid by Pan-STARRS large-scale photometric survey.[9]

Slow rotator[edit]

In February 2013, a rotational lightcurve of Thessandrus was obtained from photometric observations by American astronomer Robert Stephens at the Center for Solar System Studies (U81) in California. It gave an exceptionally long rotation period of 738±20 hours with a brightness variation of 0.60 in magnitude (U=2).[8] It belongs to the slowest rotators known to exist.

Diameter and albedo[edit]

According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, the asteroid measures 51.3 kilometers in diameter and its surface has an albedo of 0.081,[6][7] while the Collaborative Asteroid Lightcurve Link assumes a standard albedo for carbonaceous asteroids of 0.057 and calculates a somewhat larger diameter of 61.0 kilometers, as the lower the albedo (reflectivity), the larger a body's diameter at a certain absolute magnitude (brightness).[4]


This minor planet is named after Thessander (Thessandrus) from Greek mythology and Homer's Iliad. Together with 30 other Greek soldiers he hid in the Trojan horse's belly.[2] The official naming citation was published by the Minor Planet Center on 4 June 1993 (M.P.C. 22248).[10]


  1. ^ a b c d "JPL Small-Body Database Browser: 4902 Thessandrus (1989 AN2)" (2017-06-05 last obs.). Jet Propulsion Laboratory. Retrieved 20 June 2017. 
  2. ^ a b c Schmadel, Lutz D. (2007). Dictionary of Minor Planet Names – (4902) Thessandrus. Springer Berlin Heidelberg. p. 423. ISBN 978-3-540-00238-3. Retrieved 30 June 2016. 
  3. ^ a b c "4902 Thessandrus (1989 AN2)". Minor Planet Center. Retrieved 30 June 2016. 
  4. ^ a b c d e f "LCDB Data for (4902) Thessandrus". Asteroid Lightcurve Database (LCDB). Retrieved 30 June 2016. 
  5. ^ "List of Jupiter Trojans". Minor Planet Center. 20 June 2016. Retrieved 30 June 2016. 
  6. ^ 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. Bibcode:2011ApJ...741...90M. arXiv:1109.6407Freely accessible. doi:10.1088/0004-637X/741/2/90. Retrieved 30 June 2016. 
  7. ^ a b c 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. Bibcode:2012ApJ...759...49G. arXiv:1209.1549Freely accessible. doi:10.1088/0004-637X/759/1/49. Retrieved 5 December 2016. 
  8. ^ a b French, Linda M.; Stephens, Robert, D.; Coley, Daniel R.; Wasserman, Lawrence H.; Vilas, Faith; La Rocca, Daniel (October 2013). "A Troop of Trojans: Photometry of 24 Jovian Trojan Asteroids". The Minor Planet Bulletin. 40 (4): 198–203. Bibcode:2013MPBu...40..198F. ISSN 1052-8091. Retrieved 30 June 2016. 
  9. ^ a b c 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. Bibcode:2015Icar..261...34V. arXiv:1506.00762Freely accessible. doi:10.1016/j.icarus.2015.08.007. Retrieved 30 June 2016. 
  10. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 30 June 2016. 

External links[edit]