I is for Ida (Planets Aren't The Objects in Space with Moons)

Dactyl and IdaMany planets have moons. But guess what. So do some asteroids.  Just as 17th century astronomer Galileo Galilei was first to see moons around another planet, the 20th century spacecraft named in his honor was the first to discover a moon orbiting an asteroid.  In 1993 while on its way to Jupiter, NASA’s Galileo spacecraft flew right by an asteroid called Ida. It’s 19 miles wide and has a small one mile wide moon orbiting it called Dactyl. These were the first binary as...