Adrastea

Adrastea, also known as Jupiter XV, is the second by distance, and the smallest of the four inner moons of Jupiter. It was discovered in photographs taken by Voyager 2 in 1979, making it the first natural satellite to be discovered from images taken by an interplanetary spacecraft, rather than through a telescope.
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.
== Discovery and Observations ==
Adrastea was discovered by David C. Jewitt and G. Edward Danielson in Voyager 2 probe photographs taken on July 8, 1979, and received the designation S/1979 J 1.It appeared only as a dot, it was the first moon to be discovered by a spacecraft. Soon after its discovery, two other of the inner moons of Jupiter (Thebe and Metis) were observed in the images taken a few months earlier by Voyager 1.
==Physical characteristics==
Adrastea has an irregular shape and measures 20×16×14 km across. A surface area estimate would be between 840 and 1,600 (~1,200) km². This makes it the smallest of the four inner moons. The bulk, composition and mass of Adrastea are unknown, but assuming that its mean density is like that of Amalthea, around 0.86 g/cm³, its mass can assumed to be estimated at about 2 × 10¹⁵ kg.
==Orbit==
Adrastea is the smallest and second-closest member of the inner Jovian satellite family. It orbits Jupiter at a distance of about 129,000 km at the exterior edge of the planet's main ring. The orbit has very small eccentricity and inclination—around 0.0015 and 0.03°, respectively. Inclination is relative to the equator of Jupiter.
==Relationship with Jupiter's rings==
Adrastea could be a shepherd moon since it is thought to shepherd Jupiter's main ring
Category:Moons
Category:Jovian Moons
Category:Inner Moon of Jupiter
Category:Objects with No Atmosphere
Category:Objects Not in Hydrostatic Equilibrium
Category:Outer Solar System Object
Category:Prograde Satellite
Category:Numbered Objects
Category:Numbered Moons
Category:Named Moons
Category:Named Objects
Category:Shepherd Moon