It was discovered on 15 November 1990, by Belgian astronomer Eric Elst at the La Silla Observatory in northern Chile.
[1] The dark Jovian asteroid belongs to the 100 largest Jupiter trojans and has a rotation period of 17.4 hours.
[9] In July 2007, a rotational lightcurve of Thersilochos was obtained from a total of six nights of photometric observations by Italian astronomer Stefano Mottola at the Calar Alto Observatory in Spain.
[8][9] Follow-up observations in the R-band by astronomers at the Palomar Transient Factory in November 2013, and by Daniel Coley at the Center for Solar System Studies in December 2014, gave two concurring periods of 17.329 and 17.389 hours (U=3/2).
This minor planet was named from Greek mythology after the Trojan warrior Thersilochus, who fought with Hector at the battle for the dead body of Patroclus and was later slain by Achilles.