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54 Alexandra

54 Alexandra
54Alexandra (Lightcurve Inversion).png
A three-dimensional model of 54 Alexandra based on its light curve
Discovered byH. Goldschmidt
Discovery date10 September 1858
MPC designation(54) Alexandra
Named after
Alexander von Humboldt
(German explorer)
Main belt
Orbital characteristics
Epoch December 31, 2006 (JD 2454100.5)
Aphelion485.483 Gm (3.245 AU)
Perihelion326.043 Gm (2.179 AU)
405.763 Gm (2.712 AU)
1,631.620 d (4.47 a)
Physical characteristics
Dimensions160 × 135 km (± 1 km)
Mean diameter
154.137 km[1]
Mass(6.16±3.50)×1018 kg[2]
Mean density
3.50±2.11 g/cm3[2]
18.14 h[3]
Tholen = C[1]
SMASS = C[1]

Alexandra (minor planet designation: 54 Alexandra) is a carbonaceous asteroid from the intermediate asteroid belt, approximately 155 kilometers in diameter. It was discovered by German-French astronomer Hermann Goldschmidt on 10 September 1858, and named after the German explorer Alexander von Humboldt; it was the first asteroid to be named after a male.[6]


On May 17, 2005, this asteroid occulted a faint star (magnitude 8.5) and the event was observed and timed in a number of locations within the U.S. and Mexico. As a result, a silhouette profile was produced, yielding a roughly oval cross-section with dimensions of 160 × 135 km (± 1 km).[7] The mass of the asteroid can be estimated based upon the mutually perturbing effects of other bodies, yielding an estimate of (6.16±3.50)×1018 kg.[2]

Photometric observations of this asteroid during 1990–92 gave a light curve with a period of 18.14 ± 0.04 hours and a brightness variation of 0.10 in magnitude.[3] Alexandra has been studied by radar.[8] It was the namesake and largest member of the former Alexandra asteroid family; a dynamic group of C-type asteroids that share similar orbital elements. Other members included 70 Panopaea and 145 Adeona.[9] 145 Adeona was subsequently assigned to the Adeona family, with Alexandra and Panopaea being dropped.[10]


  1. ^ a b c d e f Yeomans, Donald K. "54 Alexandra". JPL Small-Body Database Browser. NASA Jet Propulsion Laboratory. Retrieved 7 April 2013.
  2. ^ a b c Carry, B. (December 2012), "Density of asteroids", Planetary and Space Science, 73, pp. 98–118, arXiv:1203.4336, Bibcode:2012P&SS...73...98C, doi:10.1016/j.pss.2012.03.009. See Table 1.
  3. ^ a b Belskaya, I. N.; et al. (November 1993), "Physical Studies of Asteroids. Part XXVII. Photoelectric Photometry of Asteroids 14 Irene, 54 Alexandra and 56 Melete", Astronomy and Astrophysics Supplement, 101 (3), pp. 507–511, Bibcode:1993A&AS..101..507B.
  4. ^ a b Hanuš, J.; et al. (May 2017), "Volumes and bulk densities of forty asteroids from ADAM shape modeling", Astronomy & Astrophysics, 601: 41, arXiv:1702.01996, Bibcode:2017A&A...601A.114H, doi:10.1051/0004-6361/201629956, A114.
  5. ^ Asteroid Data Sets Archived 2010-01-17 at WebCite
  6. ^ Schmadel, Lutz D. (2003), Dictionary of Minor Planet Names (5th ed.), Springer, p. 20, ISBN 3642297188.
  7. ^ D.W. Dunham, "Upcoming Asteroid Occultations", Sky & Telescope, June, 2006, p. 63.
  8. ^ "Radar-Detected Asteroids and Comets". NASA/JPL Asteroid Radar Research. Retrieved 30 October 2011.
  9. ^ Williams, J. G. (March 1988), "The Unusual Alexandra Family", Abstracts of the Lunar and Planetary Science Conference, 19, pp. 1277–1278, Bibcode:1988LPI....19.1277W.
  10. ^ Zappala, Vincenzo; et al. (December 1990), "Asteroid families. I - Identification by hierarchical clustering and reliability assessment", Astronomical Journal, 100, pp. 2030–2046, 2045, Bibcode:1990AJ....100.2030Z, doi:10.1086/115658. See p. 2045 and family 44.

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