Following anomalous sightings during an occultation of the star SAO 1220774 in 1978, Herculina became the first asteroid to be "confirmed" to have an asteroid moon, with the parent asteroid estimated at a 216 km diameter and a moon of about 45 km orbiting at a distance of around 1,000 km. However, careful studying in 1993, using the Hubble Space Telescope, could not locate a moon.