[3] It was discovered on 12 October 1997 by the Beijing Schmidt CCD Asteroid Program (SCAP) at Xinglong Station in the Chinese province of Hebei, and later named after the Achaean warrior Leucus from Greek mythology.

It is located in the leading Greek camp at Jupiter's L4 Lagrangian point, 60° ahead of its orbit (see Trojans in astronomy).

During spring 2013, a rotational lightcurve of Leucus was obtained from photometric observations made by astronomers Robert Stephens and Daniel Coley at the Center for Solar System Studies (CS3), California, using a 0.35/0.4-meter Schmidt-Cassegrain telescope.

In preparation for the planned visit by the Lucy spacecraft, Leucus was once again observed by astronomers Marc Buie at SwRI and Stefano Mottola at DLR in 2016.

[12][13] The Collaborative Asteroid Lightcurve Link derives a lower albedo of 0.05 and a diameter of 42.1 kilometers, in accordance with the result obtained by IRAS.