It was discovered on 17 December 1987, by astronomers Eric Elst and Guido Pizarro at the La Silla Observatory in northern Chile.
It is located in the leading Greek camp at the Gas Giant's L4 Lagrangian point, 60° ahead on its orbit (see Trojans in astronomy).
[1] This minor planet was named from Greek mythology after Actor (son of Phorbas and Hyrmine), the alleged father of the twin brothers Eurytus and Cteatus, who beat Nestor, king of Pylos, in a chariot race.
[6][9] In July and August 2015, observations by the Kepler space telescope during its K2 mission gave another two lightcurves with a concurring period of 7.28 and 7.281 hours, respectively.
[10][11] According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Actor measures 30.25 kilometers in diameter and its surface has an albedo of 0.092,[5] while the Collaborative Asteroid Lightcurve Link assumes a standard albedo for a carbonaceous asteroid of 0.057 and calculates a diameter of 36.78 kilometers based on an absolute magnitude of 10.9.