| Discovery[1] | |
|---|---|
| Discovered by | M. Wolf |
| Discovery site | Heidelberg Obs. |
| Discovery date | 31 March 1916 |
| Designations | |
| (1661) Granule | |
Named after | Edward Gall(pathologist)[2][3] |
| A916 FA · 1936 PM 1949 QG1 · 1949 SJ 1961 DB | |
| main-belt · Flora[4] | |
| Orbital characteristics[1] | |
| Epoch 4 September 2017 (JD 2458000.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 101.07 yr (36,915 days) |
| Aphelion | 2.3818AU |
| Perihelion | 1.9857 AU |
| 2.1838 AU | |
| Eccentricity | 0.0907 |
| 3.23yr (1,179 days) | |
| 121.10° | |
| 0° 18m 19.44s / day | |
| Inclination | 3.0353° |
| 261.69° | |
| 328.08° | |
| Physical characteristics | |
| Dimensions | 7.14 km(calculated)[4] |
| 24h[5] | |
| 0.24(assumed)[4] | |
| S[4][6] | |
| 12.9[1][4] · 12.99±0.22[6] | |
1661 Granule, also designatedA916 FA, is a stony Florianasteroid from the inner regions of theasteroid belt, approximately 7 kilometers in diameter. It was discovered on 31 March 1916, by German astronomerMax Wolf atHeidelberg Observatiry in southern Germany, and named for American pathologistEdward Gall.[2][7]
TheS-type asteroid is a member of theFlora family, a large collisional population of stony asteroids in theinner 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 aneccentricity of 0.09 and aninclination of 3° with respect to theecliptic.[1]Granule'sobservation arc begins with its observation atBergedorf 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]
In January 2006, the first rotationallight-curve ofGranule was obtained from photometric observations by French amateur astronomerRené Roy. It gave a longer-than averagerotation period of 24 hours with a brightness variation of 0.15magnitude (U=2).[5] No other light-curves have been obtained yet.
Granule has neither been observed by the Infrared Astronomical SatelliteIRAS, nor the JapaneseAkari satellite, nor NASA'sWide-field Infrared Survey Explorer with its subsequentNEOWISE mission. TheCollaborative Asteroid Lightcurve Link assumes an albedo of 0.24 – derived from the family's principal body and namesake, the asteroid8 Flora – and calculates a diameter of 7.14 kilometers using an absolute magnitude of 12.9.[4]
Thisminor planet was named in honor of Edward A. Gall, an internationally renowned Americanpathologist, former director of theUniversity of Cincinnati Academic Health Center and president ofUSCAP. It was named on the occasion of his retirement to commemorate his career and his discovery of theGall's granule, a feature oflymphocytes.[2][3] The officialnaming citation was published by theMinor Planet Center on 20 December 1974 (M.P.C. 3757).[8]
