Among the many thousands of named minor planets, Fanny is one of 120 asteroids for which no official naming citation has been published. All of these asteroids have low numbers, the first being 164 Eva. The last asteroid with a name of unknown meaning is 1514 Ricouxa. They were discovered between 1876 and the 1930s, predominantly by astronomers Auguste Charlois, Johann Palisa, Max Wolf and Karl Reinmuth.[13]
In 2018, from April to June, a rotational lightcurveofFanny was obtained from photometric observations over 46 nights by Frederick Pilcher at the Organ Mesa Observatory (G50) in New Mexico. Analysis gave a bimodal lightcurve with a rotation periodof236.6±0.3 hours and a brightness variation of 0.22±0.03magnitude (U=3−).[10] This determination was adopted by the Lightcurve Data base and accounts for Pilcher's observations taken between April and May. For observations taken between May and June, a similar period of 230.6±0.3 hours with a somewhat higher amplitude of 0.28±0.03 magnitude was derived (U=3−). The observer also ruled out non-principal axis rotation ("tumblin"), and considers a double period 470 hours as very unlikely.[10][a] This makes it a slow rotator, as most asteroids have much shorter periods between 2 and 20 hours. As of 2020[update], Fanny ranks among the 250th slowest rotator known to exist.
During the same apparition, Tom Polakis at the Command Module Observatory (V02) in Arizona obtained a somewhat longer period of 238.9±0.8 hours with a brightness variation of 0.24±0.03 magnitude (U=2).[14] The result supersedes an incorrect period of 5.44±0.05 hours with an amplitude of 0.01 magnitude from a tentative one-night observation by French amateur astronomers Paul Krafft, Olivier Gerteis, Hubert Gully, Luc Arnold and Matthieu Bachschmidt from 2013 (U=1).[15]
According to the surveys carried out by the Japanese Akari satellite and the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer (WISE), Fanny measures (28.77±1.00) and (28.856±0.168) kilometers in diameter and its surface has an albedo of (0.040±0.003) and (0.038±0.013), respectively.[7][8][6] The Collaborative Asteroid Lightcurve Link assumes a standard albedo for a carbonaceous C-type asteroid of 0.057 and calculates a diameter of 23.86 kilometers based on an absolute magnitude of 11.84.[9] Alternative mean-diameter measurements published by the WISE team include (30.650±0.367 km), (31.50±8.89 km), (32.42±9.57 km) and (35.82±0.35 km) with corresponding albedos of (0.0345±0.0069), (0.03±0.03), (0.03±0.02) and (0.025±0.004).[5][9]
^ abcdUsui, Fumihiko; Kuroda, Daisuke; Müller, Thomas G.; Hasegawa, Sunao; Ishiguro, Masateru; Ootsubo, Takafumi; et al. (October 2011). "Asteroid Catalog Using Akari: AKARI/IRC Mid-Infrared Asteroid Survey". Publications of the Astronomical Society of Japan. 63 (5): 1117–1138. Bibcode:2011PASJ...63.1117U. doi:10.1093/pasj/63.5.1117. (online, AcuA catalog p. 153)
^ abMasiero, Joseph R.; Grav, T.; Mainzer, A. K.; Nugent, C. R.; Bauer, J. M.; Stevenson, R.; et al. (August 2014). "Main-belt Asteroids with WISE/NEOWISE: Near-infrared Albedos". The Astrophysical Journal. 791 (2): 11. arXiv:1406.6645. Bibcode:2014ApJ...791..121M. doi:10.1088/0004-637X/791/2/121.
^Zappalà, V.; Bendjoya, Ph.; Cellino, A.; Farinella, P.; Froeschle, C. (1997). "Asteroid Dynamical Families". NASA Planetary Data System: EAR-A-5-DDR-FAMILY-V4.1. Retrieved 15 March 2020.} (PDS main page)
^Schmadel, Lutz D. (2007). "Appendix 11 – Minor Planet Names with Unknown Meaning". Dictionary of Minor Planet Names – Fifth Revised and Enlarged revision. Springer Berlin Heidelberg. pp. 927–929. ISBN978-3-540-00238-3.
