243 Ida is an S-type asteroid in the Koronis family of the main asteroid belt (MAB). It was discovered on 29 September 1884 by Austrian astronomer Johann Palisa at Vienna Observatory and named after a nymph from Greek mythology.  It has dimensions 59.8 × 25.4 × 18.6 km, and an orbit semi-major axis distance of 2.861 AU.  243 Ida is the second asteroid visited by a spacecraft and the first found to have its own moon.  Its close encounter happened on Aug. 29, 1993 as Galileo flew by at a distance of about 2,400 km en route to Jupiter.

243 Ida Information Page

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