54 Alexandra

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54 Alexandra
54Alexandra (Lightcurve Inversion).png
A three-dimensional model of 54 Alexandra based on its light curve.
Discovery[1]
Discovered by Hermann Mayer Salomon Goldschmidt
Discovery date September 10, 1858
Designations
Named after Alexander von Humboldt
Minor planet category Main belt
Orbital characteristics
Epoch December 31, 2006 (JD 2454100.5)
Aphelion 485.483 Gm (3.245 AU)
Perihelion 326.043 Gm (2.179 AU)
Semi-major axis 405.763 Gm (2.712 AU)
Eccentricity 0.196
Orbital period 1,631.620 d (4.47 a)
Average orbital speed 17.91 km/s
Mean anomaly 103.809°
Inclination 11.804°
Longitude of ascending node 313.446°
Argument of perihelion 345.594°
Physical characteristics
Dimensions 165.8[1] km
Mass (6.16 ± 3.50) × 1018[2] kg
Mean density 3.50 ± 2.11[2] g/cm3
Equatorial surface gravity 0.0463 m/s²
Escape velocity 0.0877 km/s
Rotation period 18.14[3] h
Albedo 0.056[1][4]
Temperature ~169 K
Spectral type C[1]
Absolute magnitude (H) 7.66[1]

54 Alexandra is a very large and dark main-belt asteroid. It was discovered by German-French astronomer Hermann Goldschmidt on September 10, 1858, and named after the German explorer Alexander von Humboldt; it was the first asteroid to be named after a male.[5]

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).[6]

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.[7] 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.[8] 145 Adeona was subsequently assigned to the Adeona family, with Alexandra and Panopaea being dropped.[9]

References[edit]

  1. ^ a b c d e Yeomans, Donald K. "54 Alexandra". JPL Small-Body Database Browser. NASA Jet Propulsion Laboratory. Retrieved 2013-04-07. 
  2. ^ a b Carry, B. (December 2012), "Density of asteroids", Planetary and Space Science 73: 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): 507–511, Bibcode:1993A&AS..101..507B. 
  4. ^ Asteroid Data Sets
  5. ^ Schmadel, Lutz D. (2003), Dictionary of Minor Planet Names (5th ed.), Springer, p. 20, ISBN 3642297188. 
  6. ^ D.W. Dunham, "Upcoming Asteroid Occultations", Sky & Telescope, June, 2006, p. 63.
  7. ^ "Radar-Detected Asteroids and Comets". NASA/JPL Asteroid Radar Research. Retrieved 2011-10-30. 
  8. ^ Williams, J. G. (March 1988), "The Unusual Alexandra Family", Abstracts of the Lunar and Planetary Science Conference 19: 1277-1278, Bibcode:1988LPI....19.1277W. 
  9. ^ Zappala, Vincenzo et al. (December 1990), "Asteroid families. I - Identification by hierarchical clustering and reliability assessment", Astronomical Journal 100: 2030-2046, Bibcode:1990AJ....100.2030Z, doi:10.1086/115658.  See p. 2045 and family 44.

External links[edit]