It was discovered on 3 March 1924, by German astronomer Karl Reinmuth at the Heidelberg-Königstuhl State Observatory in southwest Germany.
It orbits the Sun in the central main belt at a distance of 1.9–3.2 AU once every 4 years and 1 month (1,480 days).
[3] In May 2005, the best-rated rotational lightcurve of Arnolda was obtained from photometric observations by Australian astronomers at the Oakley Southern Sky Observatory (E09).
[9][10][a] 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, Arnolda measures between 13.68 and 16.557 kilometers in diameter and its surface has an albedo between 0.29 and 0.439.
[4][5][6][7][8] The Collaborative Asteroid Lightcurve Link derives a high albedo of 0.3760 and a diameter of 16.44 kilometers based on an absolute magnitude of 10.60.