103 Hera is a moderately large main-belt asteroid with an orbital period of 4.44 years.

It was discovered by Canadian-American astronomer James Craig Watson on September 7, 1868,[6] and named after Hera, queen and fifth in power of the Olympian gods in Greek mythology.

Photometric observations made in 2010 at the Organ Mesa Observatory at Las Cruces, New Mexico, and the Hunters Hill Observatory at Ngunnawal, Australian Capital Territory, give a synodic rotation period of 23.740±0.001 h. The bimodal light curve shows a maximum brightness variation of 0.45 ± 0.03 in magnitude.

[4] Measurements made with the IRAS observatory give a diameter of 91.58±4.14 km and a geometric albedo of 0.19±0.02.

By comparison, the MIPS photometer on the Spitzer Space Telescope gives a diameter of 88.30±8.51 km and a geometric albedo of 0.20±0.04.