1661 Granule, also designated A916 FA, is a stony Florian asteroid from the inner regions of the asteroid belt, approximately 7 kilometers in diameter. It was discovered on 31 March 1916, by German astronomer Max Wolf at Heidelberg Observatiry in southern Germany, and named for American pathologist Edward Gall.[2][7]
Classification and orbit
The S-type asteroid is a member of the Flora family, a large collisional population of stony asteroids in the inner main-belt. It orbits the Sun at a distance of 2.0–2.4 AU once every 3 years and 3 months (1,179 days). Its orbit has an eccentricity of 0.09 and an inclination of 3° with respect to the ecliptic.[1]Granule's observation arc begins with its observation at Bergedorf Observatory, one month after its official discovery observation. (It is unclear whether "HD 17", Message from Heidelberg Observatory #17, is the official discovery observation due to a different time stamp).[7]
Physical characteristics
Rotation period
In January 2006, the first rotational light-curve of Granule was obtained from photometric observations by French amateur astronomer René Roy. It gave a longer-than average rotation period of 24 hours with a brightness variation of 0.15 magnitude (U=2).[5] No other light-curves have been obtained yet.
Size estimates
Granule has neither been observed by the Infrared Astronomical Satellite IRAS, nor the Japanese Akari satellite, nor NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission. The Collaborative Asteroid Lightcurve Link assumes an albedo of 0.24 – derived from the family's principal body and namesake, the asteroid 8 Flora – and calculates a diameter of 7.14 kilometers using an absolute magnitude of 12.9.[4]
^Schmadel, Lutz D. "Appendix – Publication Dates of the MPCs". Dictionary of Minor Planet Names – Addendum to Fifth Edition (2006–2008). Springer Berlin Heidelberg. p. 221. doi:10.1007/978-3-642-01965-4. ISBN978-3-642-01964-7.