It was discovered on 5 October 1931, by German astronomer Max Wolf at Heidelberg Observatory in southwest Germany,[13] and named after Anna Risi, a model and mistress of painter Anselm Feuerbach.
[13] In September 2009, two rotational lightcurves of Nanna were obtained by American astronomer Brian Warner from photometric observations at his Palmer Divided Observatory in Colorado.
[10] These results supersede a fragmentary lightcurve taken by French amateur astronomers Federico Manzini, Laurent Bernasconi and René Roy from August 2004, which gave a period of 15.6 hours (U=1).
[4][5][6][7][8] The Collaborative Asteroid Lightcurve Link derives an albedo of 0.03 and a diameter of 35.06 kilometers with an absolute magnitude of 11.7.
[3] This minor planet was named after Anna Risi, a model in several paintings by German classicist painter Anselm Feuerbach.