Despina (astronomy)

Despina (astronomy), small satellite of the planet Neptune. Despina orbits Neptune at a distance of about 52,500 km (about 32,600 mi), completing one orbit in about eight hours. Despina’s orbit is circular and parallels Neptune’s equator.

Despina is irregular in shape, with an average diameter of about 154 km (about 96 mi), so it could fit into a large crater on the earth’s moon. Despina’s density, composition, and internal structure are unknown. Little is known of Despina’s surface except that it is almost as dark as soot. The moon is too small to hold onto an atmosphere and shows no signs of geological activity.

Despina orbits within Neptune’s ring system between rings 1989N3R and 1989N2R/1989N4R. 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 Despina’s gravity, along with the gravity of its neighbor moons Naiad and Thalassa, “shepherds” the particles in the rings by attracting and holding together the ring particles, preventing them from spreading out to form broader rings. For this reason, Despina is called a shepherd moon.

Astronomers discovered Despina in 1989 by studying images from the United States Voyager 2 spacecraft. They decided to honor Voyager 2 by crediting it with Despina’s discovery. Despina is named after a character from Greek mythology who may have been the daughter of the goddess Demeter and the god Poseidon or a Nereid, one of the fifty sea nymphs who were daughters of Doris and the god Nereus.