 In December 2010, a rotational lightcurve of "Ajax" was obtained from photometric observations taken by Robert Stephens at the Goat Mountain Astronomical Research Station in California.Lightcurve analysis gave a rotation period of 29.38 hours with a brightness variation of 0.30 magnitude (), superseding fragmentary photometric measurements by Richard P. Binzel (1988), and by Roberto Crippa and Federico Manzini (2009) at the Sozzago Astronomical Station , which gave a period of 28.4 and 34 hours, respectively ().According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the Japanese Akari satellite and the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, "Ajax" measures between 81.69 and 96.34 kilometers in diameter and its surface has an albedo between 0.048 and 0.0665.