In 2001, it was found that Patroclus is a binary object, made up of two asteroids which are almost the same size. In February, 2006, a team of astronomers led by Franck Marchis measured accurately the orbit of the system using the Keck Laser guide star adaptive optics system. They thought that the two asteroids orbit around their center of mass in 4.283±0.004 d at a distance of 680±20 km, describing a close to circular orbit. Putting together their sightings with thermal measurements taken in November 2000, the team thought what the size of the asteroids of the system could be. The slightly bigger asteroids, which measures 122 km in diameter, continues to have the name Patroclus. The smaller asteroid, measuring 112 km, is now named Menoetius (full name (617) Patroclus I Menoetius), after the legendary Patroclus's father. Its provisional designation was S/2001 (617) 1.