Asteroid moon
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Image:243 ida.jpg 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. Asteroids with moons are commonly referred to as binary asteroids. The term double asteroid is sometimes used for systems in which the asteroid and its moon are roughly the same size.
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. Other pairings may be formed when a small asteroid is captured by the gravity of a larger one.
The first asteroid moon to be identified was Dactyl which orbits 243 Ida. It was discovered by the Galileo probe in 1993. The second was discovered around 45 Eugenia in 1998. As of 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. In 2005, the asteroid 87 Sylvia was discovered to have two moons, making it the first known triple asteroid. Later the same year, the KBO 2003 EL61 was also discovered to have two moons, making it the second known KBO to have at least two moons after Pluto.
An example of a double asteroid is 90 Antiope, where two equal-sized components orbit the common centre of gravity.
Notable asteroids with moons
| Name | Orbital type | Diameter (km) (or dimensions) | Name of moon | Diameter of moon (km) (or dimensions) | Distance between pair (km) |
|---|---|---|---|---|---|
| 22 Kalliope | main belt | (231.4×175.3×146.1) | Linus | 38±6 | 1,065±8 |
| 45 Eugenia | main belt | 214.6±4.2 | Petit-Prince | 12.7±0.8 | 1,184±12 |
| 87 Sylvia | main belt | (384×264×232) | Remus | 7±2 | 706±5 |
| Romulus | 18±4 | 1,356±5 | |||
| 90 Antiope | main belt | 110±16 | S/2000 (90) 1 | 110±16 | 170±1 |
| 107 Camilla | main belt | 222.6±17.1 (325×223×139) | S/2001 (107) 1 | 9±1 | 1,235±16 |
| 121 Hermione | main belt | 209.0±4.7 (265×180×180) | S/2002 (121) 1 | 18 | 794.7±2.1 |
| 130 Elektra | main belt | 182.3±11.8 | S/2003 (130) 1 | 4 | 1,252±30 |
| 243 Ida | main belt | (59.8×25.4×18.6) | Dactyl | (1.6×1.4×1.2) | 108 |
| 283 Emma | main belt | 148.1±4.6 | S/2003 (283) 1 | 12 | 596±3 |
| 379 Huenna | main belt | 92.3±1.7 | S/2003 (379) 1 | 7 | 3,400±11 |
| 617 Patroclus | Jupiter Trojan | 105 | Menoetius | 95 | 610 |
| 762 Pulcova | main belt | 137.1±3.2 | S/2000 (762) 1 | 20 | 810 |
| 809 Lundia | main belt | ? | S/2005 (809) 1 | ? | ? |
| 854 Frostia | main belt | 15? | S/2004 (854) 1 | ? | ~50 |
| 1089 Tama | main belt | 12.9 | S/2003 (1089) 1 | 9 | 20 |
| 1313 Berna | main belt | 11 | S/2004 (1313) 1 | 11 | 35 |
| 1509 Esclangona | main belt | 12 | S/2003 (1509) 1 | 4 | 140 |
| 1862 Apollo | Apollo | 1.7 | S/2005 (1862) 1 | 0.08 | 3 |
| 3671 Dionysus | NEA | 1.5 | S/1997 (3671) 1 | 0.4 | 2.2 |
| 3749 Balam | main belt | 7 | S/2002 (3749) 1 | 1.5 | 310±20 |
| 4492 Debussy | main belt | ? | S/2004 (4492) 1 | ? | ? |
| Template:Mpl | TNO | 420? | S/2001 (26308) 1 | 170? | 11,310±110 |
| Template:Mpl | Plutino | 590? | S/2001 (47171) 1 | 250? | 7,640±460 |
| Template:Mpl | NEA | 1.2 | S/2001 (66391) 1 | 0.36 | 2.6 |
| 69230 Hermes | Apollo | ~0.4 | S/2003 (69230) 1 | ~0.4 | ~1 |
External links
| The minor planetsedit |
| Vulcanoids | Near-Earth asteroids | Main belt | Jupiter Trojans | Centaurs | Damocloids | Comets | Trans-Neptunians (Kuiper belt · Scattered disc · Oort cloud) |
| For other objects and regions, see: asteroid groups and families, binary asteroids, asteroid moons and the Solar system For a complete listing, see: List of asteroids. See also Pronunciation of asteroid names and Meanings of asteroid names. |
es:Luna asteroidal fr:Lune astéroïdale it:Satellite asteroidale ja:小惑星の衛星 pl:Księżyc planetoidy zh:小行星衛星