2895 Memnon

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2895 Memnon
Discovery [1]
Discovered by N. G. Thomas
Discovery site Anderson Mesa Stn.
Discovery date 10 January 1981
MPC designation (2895) Memnon
Pronunciation /ˈmɛmnɒn/ MEM-non
Named after
(Greek mythology)[2]
1981 AE1 · 1981 CL
Jupiter trojan[3]
(Trojan camp)[4]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc 39.49 yr (14,424 days)
Aphelion 5.5000 AU
Perihelion 4.9799 AU
5.2400 AU
Eccentricity 0.0496
11.99 yr (4,381 days)
0° 4m 55.92s / day
Inclination 27.210°
Jupiter MOID 0.1263 AU
Jupiter Tisserand parameter 2.7760
Physical characteristics
Dimensions 55.67 km (calculated)[5]
56.706±0.200 km[6][7]
7 h (fragmentary)[8]
7.5 h (from 1980s)[9]
7.502±0.010 h[10]
7.509±0.006 h[11][a]
7.52±0.01 h[b]
7.55±0.01 h[12][a]
0.057 (assumed)[5]
B–V = 0.680±0.060[13]
V–R = 0.380±0.040[13]
V–I = 0.710±0.044[13]
9.9[6][7] · 10.0[1][5] · 10.09±0.22[14]

2895 Memnon (/ˈmɛmnɒn/ MEM-non), provisional designation 1981 AE1, is a carbonaceous Jupiter trojan from the Trojan camp, approximately 56 kilometers in diameter. It was discovered on 10 January 1981, by American astronomer Norman Thomas at Lowell's Anderson Mesa Station near Flagstaff, Arizona, United States.[3] It was named after Memnon from Greek mythology.[2]

Orbit and classification[edit]

Memnon is a Trojan asteroid that resides in the Trojan camp of Jupiter's L5 Lagrangian point, which lies 60° behind the gas giant's orbit (see Trojans in astronomy).[4] It orbits the Sun in the outer main-belt at a distance of 5.0–5.5 AU once every 11 years and 12 months (4,381 days). Its orbit has an eccentricity of 0.05 and an inclination of 27° with respect to the ecliptic.[1] Due to a precovery taken at the Australian Siding Spring Observatory in 1977, Memnon's observation arc begins 4 years prior to its official discovery observation.[3]

Physical characteristics[edit]

Memnon has been characterized as a carbonaceous C-type asteroid.[5]


A first rotational lightcurve of Memnon was obtained by American astronomer Richard Binzel in the early 1980s. It gave a rotation period of 7.5 hours with a brightness variation of 0.24 magnitude (U=2).[9] In February 2005, a fragmentary lightcurve by Italian astronomer Federico Manzini at the Stazione Astronomica di Sozzago (A12) gave a period of 7 hours (U=1).[8]

The so-far best rated lightcurve was obtained by Italian ESO astronomer Stefano Mottola in November 1990, which gave a period of 7.502 hours with an amplitude of 0.22 magnitude (U=3-).[10]

In January 2015 and 2016, photometric observations by American astronomer Robert Stephens at the Center for Solar System Studies (CS3, U81) gave a period of 7.55 and 7.509 hours, with a brightness variation of 0.33 and 0.08, respectively (U=2/n.a.),[11][12][a] while his college, Dan Coley, obtained a concurring period of 7.52 hours with an amplitude of 0.14 magnitude at DanHenge Observatory (CS3, U80) in January 2017 (U=n.a.).[b]

Diameter and albedo[edit]

According to the survey carried out by NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Memnon measures 56.70 kilometers in diameter, and its surface has an albedo of 0.060,[6][7] while the Collaborative Asteroid Lightcurve Link assumes a standard albedo for carbonaceous asteroids of 0.057 and calculates a diameter of 55.67 kilometers, with an absolute magnitude of 10.0.[5]


This minor planet was named for Memnon from Greek mythology. He was the king of Ethiopia and nephew of king Priam of Troy. He supported the Trojan side in the Trojan War with 10,000 men and was killed in combat by Achilles.[2] The official naming citation was published by the Minor Planet Center on 20 December 1983 (M.P.C. 8405).[15]


  1. ^ a b c Stephens (2015/16): lightcurve plots of (2895) Memnon taken in (2015) and (2016) by Robert Stephens at the CS3-Trojan Station, Landers (U81). Summary figures at Collaborative Asteroid Lightcurve Link (CALL)
  2. ^ a b Coley (2017): lightcurve plot of (2895) Memnon by Daniel Coley at the CS3-DanHenge Observatory, Landers (U80), with a rotation period 7.52±0.01 hours with a brightness amplitude of 0.14 mag.


  1. ^ a b c d "JPL Small-Body Database Browser: 2895 Memnon (1981 AE1)" (2017-06-04 last obs.). Jet Propulsion Laboratory. Retrieved 14 June 2017. 
  2. ^ a b c Schmadel, Lutz D. (2007). Dictionary of Minor Planet Names – (2895) Memnon. Springer Berlin Heidelberg. p. 238. ISBN 978-3-540-00238-3. Retrieved 27 December 2016. 
  3. ^ a b c "2895 Memnon (1981 AE1)". Minor Planet Center. Retrieved 27 December 2016. 
  4. ^ a b "List of Jupiter Trojans". Minor Planet Center. 20 June 2016. Retrieved 27 December 2016. 
  5. ^ a b c d e f "LCDB Data for (2895) Memnon". Asteroid Lightcurve Database (LCDB). Retrieved 27 December 2016. 
  6. ^ 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. Bibcode:2012ApJ...759...49G. arXiv:1209.1549Freely accessible. doi:10.1088/0004-637X/759/1/49. Retrieved 27 December 2016. 
  7. ^ 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 27 December 2016. 
  8. ^ a b Behrend, Raoul. "Asteroids and comets rotation curves – (2895) Memnon". Geneva Observatory. Retrieved 27 December 2016. 
  9. ^ a b Binzel, Richard P.; Sauter, Linda M. (February 1992). "Trojan, Hilda, and Cybele asteroids - New lightcurve observations and analysis". Icarus: 222–238. Bibcode:1992Icar...95..222B. ISSN 0019-1035. doi:10.1016/0019-1035(92)90039-A. Retrieved 27 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 27 December 2016. 
  11. ^ a b Stephens, Robert D.; Coley, Daniel R.; French, Linda M. (July 2016). "A Report from the L5 Trojan Camp - Lightcurves of Jovian Trojan Asteroids from the Center for Solar System Studies". The Minor Planet Bulletin. 43 (3): 265–270. Bibcode:2016MPBu...43..265S. ISSN 1052-8091. Retrieved 27 December 2016. 
  12. ^ 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 27 December 2016. 
  13. ^ a b c 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. Retrieved 14 June 2017. 
  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. Bibcode:2015Icar..261...34V. arXiv:1506.00762Freely accessible. doi:10.1016/j.icarus.2015.08.007. Retrieved 27 December 2016. 
  15. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 27 December 2016. 

External links[edit]