Galatea (astronomy)

Galatea (astronomy), small satellite of the planet Neptune. Galatea orbits Neptune at a distance of about 62,000 km (about 38,500 mi). Galatea completes one orbit of Neptune every ten hours. Its orbit is circular and parallels Neptune’s equator.

Galatea is irregular in shape, with an average diameter of about 180 km (about 108 mi), so it could fit into a large crater on Earth’s moon. The moon’s density, composition, and internal structure are unknown. Little is known of its surface except that it is almost as dark as soot. Galatea is too small to hold onto an atmosphere and shows no signs of geological activity.

Galatea orbits within Neptune’s ring system between rings 1989N4R and 1989N1R. Neptune’s rings are made up of particles of ice and dust forming broad and narrow rings and ring arcs, or apparently incomplete rings. Scientists believe that Galatea’s gravity “shepherds” the particles in the rings by attracting them and holding them together to prevent them from spreading out to form broader rings. For this reason, Galatea is called a shepherd moon.

Astronomers discovered Galatea in 1989 by studying photos from the United States Voyager 2 spacecraft. They decided to honor the spacecraft by crediting it with Galatea’s discovery. Galatea is named for a Nereid, or sea nymph, who was one of fifty daughters of the god Nereus and Doris in Greek mythology.