Adrastea (moon)
Not to be confused with the asteroid called 5 Astraea
Image of Adrastea taken by Galileo spacecraft between November 1996 and June 1997 |
|
| Discovery | |
|---|---|
| Discovered by |
|
| Discovery date | July 8, 1979 |
| Designations | |
| Adjective | Adrastean |
| Orbital characteristics | |
| Mean orbit radius | 129,000 km |
| Eccentricity | 0.0015 |
| Orbital period | 0.29826 d (7 h 9.5 min) |
| Average orbital speed | 31.378 km/s |
| Inclination | 0.03° (to Jupiter's equator) |
| Satellite of | Jupiter |
| Physical characteristics | |
| Dimensions | 20×16×14 km |
| Mean radius | 8.2 ± 2.0 km |
| Volume | ~2,345 km³ |
| Mass | ~2 × 1015 kg |
| Mean density | 0.86 g/cm³ (assumed) |
| Equatorial surface gravity | ~0.002 m/s² (0.0004 g) |
| Escape velocity | ~0.008 km/s |
| Rotation period | synchronous |
| Axial tilt | zero |
| Albedo | 0.1 ± 0.045 |
| Temperature | ~122 K |
Adrastea ( /ˌædrəˈstiːə/ AD-rə-STEE-ə; Greek: Αδράστεια), also known as Jupiter XV, is the second by distance, and the smallest of the four inner moons of Jupiter. It was discovered in Voyager 2 probe photographs taken in 1979, making it the first natural satellite to be discovered from images taken by an interplanetary spacecraft, rather than through telescopic photography. It was officially named after the mythological Adrasteia, foster mother of the Greek god Zeus—the equivalent of the Roman god Jupiter.
Adrastea is one of the few moons in the Solar System known to orbit its planet in less than the length of that planet's day. It orbits at the edge of Jupiter's Main Ring and is thought to be the main contributor of material to the Rings of Jupiter. Despite observations made in the 1990s by the Galileo spacecraft, very little is known about the moon's physical characteristics other than its size and the fact that it is tidally locked to Jupiter.
Read more about Adrastea (moon): Discovery and Observations, Physical Characteristics, Orbit, Relationship With Jupiter's Rings