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The asteroid 4769 Castalia (previously known by the provisional designation 1989 PB) was the first asteroid to be directly imaged. It is an Apollo, Mars- and Venus-crosser asteroid. It was discovered on August 9, 1989 by Eleanor F. Helin (Caltech) on photographic plates taken at Palomar Observatory. It is named after Castalia, a nymph in Greek mythology.
General information Castalia's orbit took it within eleven lunar distances of Earth, allowing it to be observed with radar from the Arecibo Observatory by Scott Hudson (Washington State University) and Steven J. Ostro (JPL). The data allowed Hudson et al. to produce a three-dimensional model of the object. Castalia has a peanut shape, suggesting two ~800 m diameter pieces held together by their weak mutual gravity. Since then radar observations of other asteroids have found other contact binaries. See also | ||||||||
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