Adrastea (moon) - Definition and Overview

Adrastea

This image of Adrastea was taken by Galileo's solid state imaging system between November 1996 and June 1997.
Discovery
Discovered by	David C. Jewitt G. Edward Danielson
Discovered on	July 8 1979
Orbital characteristics
Mean radius	129,000 km
Eccentricity	0.0018
Revolution period	7h 9.5m
Inclination	0.05°
Is a satellite of	Jupiter
Physical characteristics
Mean diameter	16.4 km
Surface area	km2
Mass	1.8894×1016 kg
Mean density	4.5 g/cm3
Surface gravity	0.012 m/s2
Surface Gravity (Earth = 1)	0.00122
Rotation period	7h 9.5m
Axial tilt	0°
Albedo	0.05
Surface temp.	min mean max K K K
Atmospheric pressure	0 kPa

Adrastea ("a DRAS tee a") is the second of Jupiter's known moons (counting outward from the planet). It was discovered on Voyager 2 probe photographs taken in 1979 and received the designation S/1979 J 1 (IAUC 3454 (http://cfa-www.harvard.edu/iauc/03400/03454.html)) after the discovery had been announced in Science (vol. 206, p. 951, November 23, 1979). In 1983 it was officially named after the mythological Adrastea, daughter of Jupiter and Ananke.

It belongs to the Amalthea group of small inner jovian moons.

Adrastea 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.

Discovery image of Adrastea, taken on July 8, 1979 by Voyager 2. Adrastea is the dot in the very middle, straddling the line of the Jovian rings.