In March 2018, a rotational lightcurveofNora was obtained from photometric observations by Tom Polakis at the Command Module Observatory (V02) in Arizona. Lightcurve analysis gave a rotation periodof55.53±0.08 hours with a low brightness variation of 0.08±0.02magnitude (U=2).[10] 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 24 h and 34.4±0.5 h with an amplitude of 0.2 and 0.08±0.02 magnitude, respectively (U=1/2−).[12][13] In April 2007, French astronomer Arnaud Leroy determined a period of 9.6 h and a brightness variation of 0.01 magnitude (U=1).[14]
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 (38.719±0.105), (39.58±0.62) and (40.02±0.8) kilometers in diameter and its surface has an albedo of (0.068±0.012), (0.065±0.002) and (0.0635±0.003), respectively.[7][8][9] The Collaborative Asteroid Lightcurve Link derives an albedo of 0.0404 and a diameter of 39.84 kilometers based on an absolute magnitude of 11.1.[11] Alternative mean-diameter measurements published by the WISE team include (41.712±11.25 km), (42.407±0.229 km), (43.41±12.97 km), (43.43±5.49 km) and (46.96±11.00 km) with corresponding albedos of (0.0299±0.0194), (0.0565±0.0056), (0.028±0.017), (0.034±0.009) and (0.025±0.011).[5][11] On 4 May 2004, an asteroid occultationofNora gave a best-fit ellipse dimension of (40.0 km × 40.0 km), with a poor quality rating of 1. These timed observations are taken when the asteroid passes in front of a distant star.[5]
^Lagerkvist, C. -I.; Magnusson, P.; Debehogne, H.; Hoffmann, M.; Erikson, A.; de Campos, A.; et al. (November 1992). "Physical studies of asteroids. XXV - Photoelectric photometry of asteroids obtained at ESO and Hoher List Observatory". Astronomy and Astrophysics Supplement Series. 95 (3): 461–470. Bibcode:1992A&AS...95..461L. ISSN0365-0138.
^Florczak, M.; Dotto, E.; Barucci, M. A.; Birlan, M.; Erikson, A.; Fulchignoni, M.; et al. (November 1997). "Rotational properties of main belt asteroids: photoelectric and CCD observations of 15 objects". Planetary and Space Science. 45 (11): 1423–1435. Bibcode:1997P&SS...45.1423F. doi:10.1016/S0032-0633(97)00121-9. ISSN0032-0633.