Leda (astronomy)

Leda (astronomy), small satellite of the planet Jupiter. Leda orbits Jupiter at an average distance of about 11 million km (about 6.6 million mi), completing one orbit in about 239 Earth days. Leda’s orbit is shaped like an oval and is tilted about 27° to Jupiter’s equator.

Leda is thought to have an irregular shape but probably measures about 16 km (about 9.6 mi) across. The smallest satellite known to orbit Jupiter, Leda could easily fit inside a medium-sized crater on the earth’s moon. No spacecraft has flown past Leda, so it has never been studied closely. Little is known of Leda’s interior structure or composition, though its density indicates that it is more rock than ice. Leda is the innermost of four moons with similar orbits around Jupiter and similar density. They are called the a moons because their names end with the letter a. Astronomers theorize that the a moons started as an asteroid orbiting the sun about four billion years ago. The asteroid flew through the dense dust cloud surrounding Jupiter. Collisions with particles within the cloud slowed and shattered the asteroid. The four largest fragments were slowed enough to be captured by Jupiter’s gravity and become the a moons.

American astronomer Charles Kowal discovered Leda in 1974. The moon is named for a character in Greek mythology, Leda, who was the queen of Sparta. Leda was a paramour of the god Zeus, whom the Romans renamed Jupiter. Leda and Zeus were the parents of Helen of Troy and Pollux.