[2] Hopmann is a dark C-type asteroid that orbits the Sun in the outer main-belt at a distance of 2.6–3.6 AU once every 5 years and 6 months (2,014 days).

[11] According to the survey carried out by the Infrared Astronomical Satellite IRAS, Hopmann measures 35.51 kilometers in diameter.

[1] The Collaborative Asteroid Lightcurve Link agrees with the Supplemental IRAS Minor Planet Survey (SIMPS) data and derives an albedo of 0.039 and a diameter of 35.47 kilometers,[3] while observations with NASA's Wide-field Infrared Survey Explorer and its subsequent NEOWISE mission gave an albedo of 0.06 and a diameter of 44.33 kilometers.

The lightcurves gave a well-defined rotation period of 17.476, 17.478 and 17.480 hours, respectively, with a brightness variation between 0.36 and 0.44 magnitude (U=3/3/3-).

[5][6][8] In 2016, a re-modeled lightcurve, constructed from data compiled in the Lowell Photometric Database, also gave a concurring period.