 In March 2005, a rotational lightcurve of "Sonneberga" was obtained by French amateur astronomer Laurent Bernasconi.Lightcurve analysis gave a longer-than average rotation period of 34.2 hours with a brightness variation of 0.41 magnitude ().According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the Japanese Akari satellite, and the NEOWISE mission of the WISE space-telescope, "Sonneberga" measures between 30.17 and 36.70 kilometers in diameter, and its surface has an albedo between 0.042 and 0.059.