Hektor is one of the most stretched bodies of its size in the solar system, being 370 × 200 km. It is thought that Hektor might be a contact binary (two asteroids joined by gravitational attraction) like 216 Kleopatra. Hubble Space Telescope sightings of Hektor in 1993 did not show an obvious stretched shape because of a limited angular resolution. On July 17, 2006, the Keck-10m II telescope and its Laser guide star Adaptive Optics (AO) system indicated a stretched shape for Hektor. Additionally, since this AO system provides an excellent and stable correction (angular resolution of 0.060 arcsec in K band), a 15-km moon at 1000 km from Hektor was found. The moon's provisional designation is S/2006 (624) 1. Hektor is, so far, the only known binary Trojan asteroid in the L4 point and the first Trojan with a moon. 617 Patroclus, another big Trojan asteroid in the L5, is made of two same-sized asteroids.