Discovery date September 10, 1858 Aphelion 485.483 Gm (3.245 AU) Semi-major axis 405.763 Gm (2.712 AU) Orbits Sun Discovery site Paris Observatory | Minor planet category Main belt Perihelion 326.043 Gm (2.179 AU) Discovered 10 September 1858 | |
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Discovered by Hermann Mayer Salomon Goldschmidt Similar Hermann Goldschmidt discoveries, Other celestial objects | ||
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.
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).
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. Alexandra has been studied by radar. 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. 145 Adeona was subsequently assigned to the Adeona family, with Alexandra and Panopaea being dropped.