54 Alexandra

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.^[7]

54 Alexandra

A three-dimensional model of 54 Alexandra based on its light curve
Discovery[1]
Discovered by	H. Goldschmidt
Discovery date	10 September 1858
Designations
MPC designation	(54) Alexandra
Pronunciation	/ˌælɪɡˈzændrə, -ˈzɑːn-/ AL-ig-ZA(H)N-drə[2]
Named after	Alexander von Humboldt (German explorer)
Minor planet category	Main belt
Adjectives	Alexandrian
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 (sidereal)	1,631.620 d (4.47 a)
Mean anomaly	103.809°
Inclination	11.804°
Longitude of ascending node	313.446°
Argument of perihelion	345.594°
Physical characteristics
Dimensions	160 × 135 km (± 1 km)
Mean diameter	154.137 km[1]
Mass	(6.16±3.50)×1018 kg[3]
Mean density	3.50±2.11 g/cm3[3]
Synodic rotation period	18.14 h[4]
Pole ecliptic longitude	17°±3°[5]
Pole ecliptic latitude	155°±4°[5]
Geometric albedo	0.056[1][6]
Spectral type	Tholen = C[1] SMASS = C[1]
Absolute magnitude (H)	7.66[1]

Description

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).^[8] 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.^[3]

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.^[4] Alexandra has been studied by radar.^[9] 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.^[10] 145 Adeona was subsequently assigned to the Adeona family, with Alexandra and Panopaea being dropped.^[11]

In popular culture

In the Swedish film Aniara, it is mentioned that 54 Alexandra is the closest celestial body which the off-course and out-of-control spacecraft will approach before it leaves the Solar System.