Sinope (astronomy)

Sinope (astronomy), small satellite of the planet Jupiter. Sinope orbits Jupiter at an average distance of 23.7 million km (14.2 million mi), completing one orbit in about 758 Earth days. Sinope’s orbit is elliptical and is tilted about 30° to Jupiter’s equator. Sinope has a retrograde orbit, which means that it moves clockwise as seen from Jupiter’s north pole. Most moons and planets in the solar system, including Jupiter’s 12 inner moons, travel counterclockwise as seen from the north pole of the body they orbit.

Sinope measures about 36 km (about 22 mi) across, so it could easily fit inside a medium-sized crater on the earth’s moon. Little is known of Sinope’s interior structure or composition, though its density indicates that it is more rock than ice. Sinope is one of four moons with similar density and similar orbits around Jupiter. They are called the e moons because their names end with that letter. Astronomers theorize that the e moons started as an asteroid orbiting the sun about 4 billion years ago. The asteroid flew through the dense dust cloud surrounding Jupiter. Collisions with particles in the cloud slowed and shattered the asteroid. The four largest fragments were slowed enough to be captured by Jupiter’s gravity and become the e moons.

American astronomer Seth Nicholson discovered Sinope in 1914. The moon is named for a character in Greek mythology who was one of the few women unsuccessfully courted by Zeus, whom the Romans renamed Jupiter.