About 20 percent of asteroids have moons, and some have more than one. Five asteroids in the asteroid belt have two moons, including the asteroids named 93 Minerva, 87 Sylvia and 45 Eugenia. Researchers can use information about an asteroid's moon to find out more about the asteroid itself, because they often have the same origins. One exception to this is 93 Minerva, because it is much more dense than other multi-moon asteroids.
More facts about asteroids:
- The first asteroid moon ever discovered is called Dactyl, an it is the moon of 243 Ida. It was discovered in 1993 by the spacecraft Galileo and was the second asteroid ever to be visited by a spacecraft.
- When an asteroid and its moon are roughly the same size, they can be called a double asteroid system. An example of this is the 90 Antiope system. Both 90 Antiope and its moon are about 55 miles in diameter (about 88 km), and both parts are among the 500 largest known asteroids.
- There are at least 47 asteroids with known moons or satellites in the asteroid main belt alone.