August 10, 2005—It sounds like a junkyard rust-bucket, and it's parked about 325 million miles (523 million kilometers) from Earth. But astronomers say 87 Sylvia is part of something special: the first triple asteroid system ever observed.

Scientists know of some 60 asteroid pairs locked in twin orbits. However, today's announcement by astronomers in the United States and France marks the first time researchers have observed two smaller asteroids, or moonlets, in orbit around a third, larger asteroid.

First spotted in 1866, 87 Sylvia spins in the asteroid belt between Mars and Jupiter. Scientists believe the potato-shaped, "rubble-pile" asteroid formed after two older asteroids collided. Sylvia's gravity likely lassoed other impact debris, pulling its two mini-moons into orbit.

Astronomers have dubbed the two moonlets Romulus and Remus.

—Sean Markey

• See More Photos in the News
• See Today's Top Stories