Ida-2(ÿ -dă) An asteroid that was discovered in 1880. It is an S-type asteroid, studied by the Galileo spacecraft in 1993, when it was found to have a satellite, named Dactyl . Ida is about 58 km × 23 km. Dactyl is about 1.5 km in diameter and orbits Ida at a distance of about 100 km.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006