Asteroid moon
An asteroid moon is an asteroid that orbits another asteroid. It is thought that many asteroids may possess moons, in some cases quite substantial in size. An asteroid whose moon is roughly the same size as the asteroid itself may be referred to as a binary asteroid.The origin of asteroid moons is not currently known with certainty, and a variety of possibilities exist. A widely accepted theory is that asteroid moons are formed from debris knocked off of the primary asteroid by an impact.
The first asteroid moon known is Dactyl which orbits 243 Ida. It was discovered by the Galileo probe in 1993. The second moon was discovered around 45 Eugenia in 1999. By February, 2004, nearly 37 more asteroid moons had been discovered by Earth-bound telescopes. Asteroid moons have been discovered orbiting main belt asteroids, Trojan asteroids, near-Earth objects, and Kuiper Belt objects.
An example of a binary asteroid is 90 Antiope, where two equal-sized components orbit each other.
| Name | Orbital type | Diameter (km) | Name of Moon | Diameter of Moon (km) | Distance between pair (km) |
|---|---|---|---|---|---|
| 22 Kalliope | main belt | 181 | Linus | 38 | 1,063 |
| 45 Eugenia | main belt | 215 | Petit-Prince | 13 | 1,190 |
| 87 Sylvia | main belt | 261 | S/2001 (87) 1 | 15 | 1,370 |
| 90 Antiope | main belt | 85 | S/2000 (90) 1 | 85 | 170 |
| 107 Camilla | main belt | 223 | S/2001 (107) 1 | 9 | 1,000 |
| 121 Hermione | main belt | 209 | S/2002 (121) 1 | 13 | 795 |
| 243 Ida | main belt | 108 | Dactyl | 1.4 | 108 |
| 283 Emma | main belt | 148 | S/2003 (283) 1 | 12 | 370 |
| 617 Patroclus | Jupiter Trojan | 105 | S/2001 (617) 1 | 95 | 610 |
| 762 Pulcova | main belt | 137 | unnamed | 20 | 810 |
| 1509 Esclangona | main belt | 12 | unnamed | 20 | 810 |
| 3671 Dionysus | near-Earth asteroid | 7 | S/2003 (1509) 1 | 0.4 | 140 |
| 3749 Balam | main belt | 1.5 | S/2002 (3749) 1 | 1.5 | 350 |
| (26308) 1998 SM165 | TNO | 465 | S/2001 (26308) 1 | 180 | 6,000 |
| (47171) 1999 TC36 | Plutino | 680 | S/2001 (47171) 1 | 290 | 8,000 |
| (66391) 1999 KW4 | near-Earth asteroid | 1.2 | S/1997 (3671) 1 | 0.4 | 2.2 |
| The Solar System |
| Sun | Mercury | Venus | Earth | Moon | Mars | Asteroids | Jupiter | Saturn | Uranus | Neptune | Pluto |
| (For other objects and regions, see: List of solar system objects, Astronomical objects) |