783 Nora (prov. designation: or ) is a dark background asteroid from the inner regions of the asteroid belt. It was discovered by Austrian astronomer Johann Palisa at the Vienna Observatory on 18 March 1914. The carbonaceous C-type asteroid has a longer-than average rotation period of 55.5 hours and measures approximately in diameter. It was likely named after Nora Helmer, principal character in the play A Doll's House by Norwegian poet Henrik Ibsen. Orbit and classification Nora is a non-family asteroid of the main belt's background population when applying the hierarchical clustering method to its proper orbital elements. It orbits the Sun in the inner asteroid belt at a distance of 1.8–2.9 AU once every 3 years and 7 months (1,310 days; semi-major axis of 2.34 AU). Its orbit has an eccentricity of 0.23 and an inclination of 9° with respect to the ecliptic. The body's observation arc begins with its first observation as at Heidelberg Observatory on 28 August 1911, more than two years prior to its official discovery observation at Vienna Observatory. Naming This minor planet was likely named after Nora Helmer, the heroine in the play A Doll's House (1879) by Norwegian poet Henrik Ibsen (1828–1906). The name was given by the discoverer's friends. The was also mentioned in The Names of the Minor Planets by Paul Herget in 1955 (). Physical characteristics In the Bus–Binzel SMASS classification, Nora is a common, carbonaceous C-type asteroid. In the Tholen classification it is one of few asteroids considered unclassifiable. Rotation period In March 2018, a rotational lightcurve of Nora was obtained from photometric observations by Tom Polakis at the Command Module Observatory in Arizona. Lightcurve analysis gave a rotation period of hours with a low brightness variation of magnitude (). The result supersedes previous observations by European astronomers at the La Silla, Haute Provence and Hoher List observatories during the 1990s which gave two periods of and with an amplitude of and magnitude, respectively (). In April 2007, French astronomer Arnaud Leroy determined a period of and a brightness variation of 0.01 magnitude (). Diameter and albedo According to the surveys carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer (WISE), the Japanese Akari satellite, and the Infrared Astronomical Satellite IRAS, Nora measures (), () and () kilometers in diameter and its surface has an albedo of (), () and (), respectively. The Collaborative Asteroid Lightcurve