Adrastea ("a DRAS tee uh") is the second of Jupiter's known moons. It was discovered by the Voyager 1 probe and is named after the daughter of Jupiter and Ananke (or possibly for the mythical Greek king of Argos named Adrastus, who led several primitive expeditions against Thebes and whose daughter married Polynices of Thebes). It is inside Jupiter's planetary ring and may be the source of some of its material. Its orbit lies inside Jupiter's synchronous orbit radius, and as a result tidal forces are slowly causing its orbit to decay. It is also within Jupiter's Roche limit, but is small enough to avoid tidal disruption.
- Orbital radius: 129,000 km
- Diameter: 20 km (23 x 20 x 15)
- Mass: 1.91*1016kg
- Orbital period: 7.11 hours
- Orbital inclination: 0°