4324 Bickel, provisional designation 1981 YA1, is a stony asteroid from the middle region of the asteroid belt, approximately 12 kilometers in diameter. It was discovered on 24 December 1981, by American astronomer Laurence Taff at Lincoln Laboratory's Experimental Test Site in Socorro, New Mexico, United States. The asteroid was named after amateur astronomer Wolf Bickel.[2]
Bickel orbits the Sun in the central main-belt at a distance of 2.0–3.1 AU once every 4 years and 1 month (1,483 days). Its orbit has an eccentricity of 0.20 and an inclination of 8° with respect to the ecliptic.[1] It was first identified as A924 YCatHeidelberg Observatory in 1924, extending the body's observation arc by 57 years prior to its official discovery observation at Socorro.[2]
In September 2001, the first ever conducted photometric observation of Bickel at the Rozhen Observatory, Bulgaria, rendered a rotational lightcurve with a longer-than-average periodof26.5 hours and a brightness variation of 0.63 magnitude (U=2).[6] A more refined lightcurve was obtained in October 2005, by astronomers Raymond Poncy, Laurent Bernasconi and Rui Goncalves, which gave a well-defined period of 26.592±0.003 hours with an amplitude of 0.72 magnitude (U=3).[5]
According to observations by NASA's space-based Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Bickel measures 11.7 kilometers in diameter and its surface has an albedo of 0.248,[3] while the Collaborative Asteroid Lightcurve Link assumes a standard albedo for stony asteroids of 0.20 and calculates a slightly larger diameter of 12.4 kilometers with an absolute magnitude of 11.9.[4]
At the time this minor planet was named, he had discovered more than 540 numbered minor planets.[2] The official naming citation was published by the Minor Planet Center on 22 July 2013 (M.P.C. 84378).[8] Bickel has become Germany's most prolific discoverer of asteroids, ahead of (professional) astronomer Freimut Börngen, the first time in 150 years, that an amateur astronomer is ranking first among the German top discoverers.[9] His total number of discoveries has since increased to more than 600.[10]
