| Discovery[1] | |
|---|---|
| Discovered by | Y. Mizuno T. Furuta |
| Discovery site | Kani Obs. (403) |
| Discovery date | 21 January 1990 |
| Designations | |
| (4951) Iwamoto | |
Named after | Masayuki Iwamoto (Japanese astronomer)[2] |
| 1990 BM · 1931 UQ 1985 QN6 · 1985 RH5 1989 WS3 | |
| main-belt · (inner)[3] | |
| Orbital characteristics[1] | |
| Epoch 4 September 2017 (JD 2458000.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 85.45 yr (31,210 days) |
| Aphelion | 2.6318AU |
| Perihelion | 1.8824 AU |
| 2.2571 AU | |
| Eccentricity | 0.1660 |
| 3.39yr (1,239 days) | |
| 79.093° | |
| 0° 17m 26.52s / day | |
| Inclination | 7.5269° |
| 101.08° | |
| 339.95° | |
| Knownsatellites | 1[4][a](≥ 0.76 Ds/Dp;P: 118 h) |
| Physical characteristics | |
| Dimensions | 4.39±0.02 km[4] 5.192±0.043 km[5] 5.515±0.033 km[6] 5.528 km(revised WISE)[7] 5.53 km(taken)[3] |
| 118 h[8] 118.0±0.2h[b] | |
| 0.1844(revised WISE)[7] 0.1859±0.0324[6] 0.218±0.038[5] | |
| SMASS =S[1] · S[3] V–R =0.480±0.030[b] | |
| 13.3[1] · 13.74±0.06[3][7][b] · 13.74[6] · 14.01±1.40[9] | |
4951 Iwamoto, provisional designation1990 BM, is a stony, synchronousbinary[a]asteroid andslow rotator from theinner regions of theasteroid belt, approximately 5.5 kilometers in diameter. It was discovered on 21 January 1990, by Japanese astronomersYoshikane Mizuno andToshimasa Furuta at Kani Observatory (403) in Japan.[10]
Iwamoto orbits the Sun in theinner main-belt at a distance of 1.9–2.6 AU once every 3 years and 5 months (1,239 days). Its orbit has aneccentricity of 0.17 and aninclination of 8° with respect to theecliptic.[1] It was first identified as1931 UQ atLowell Observatory in 1931, extending the body'sobservation arc by 59 years prior to its official discovery observation at Kani.[10]
In theSMASS classification,Iwamoto is a commonS-type asteroid.[1]
According to the survey carried out by NASA'sWide-field Infrared Survey Explorer with its subsequentNEOWISE mission,Iwamoto measures 5.192 and 5.515 kilometers in diameter, and its surface has analbedo of 0.218 and 0.186, respectively.[6][5] TheCollaborative Asteroid Lightcurve Link adoptsPetr Pravec's revised WISE-data, that is, an albedo of 0.1844 and a diameter of 5.528 kilometers with on anabsolute magnitude of 13.74.[3][7]
From 25 December 2006 to 23 March 2007, photometric observations ofIwamoto were obtained by the international community of photometrists at Badlands Observatory (SD, USA),Ondřejov Observatory (Czech Republic),Modra Observatory (Slovakia), Carbuncle Hill Observatory (RI, USA), Sonoita Research Observatory (AZ, USA), Kharkiv Observatory (Ukraine),McDonald Observatory (TX, USA), Ironwood Observatory (HI, USA), Leura Observatory (Australia),Skalnaté pleso Observatory (Slovakia), Shed of Science Observatory (MN, USA),Pic du Midi Observatory (France).[a]
Lightcurve analysis gave arotation period of 118 hours with a brightness variation of 0.34magnitude (U=3).[b] In May 2011, astronomers Etienne Morelle,Raoul Behrend obtained another lightcurve with a concurring period of 118 hours and an amplitude of 0.38 magnitude.(U=3).[8] With such a long period,Iwamoto is also aslow rotator, as the vast majority of asteroids have a much shorter rotation period of 2.2 to 20 hours.
During the photometric observations in 2006/7, it was revealed thatIwamoto ("primary") is a synchronousbinary system with aminor-planet moon ("secondary") orbiting it every 4.917 days (or 118 hours, which identical to the primary's rotation). Based on the secondary-to-primary mean-diameter ratio (Ds/Dp) of at least 0.76, it was estimated thatIwamoto and its moon measure 4.0 and 3.5 kilometers, respectively.[b] The diameter ofIwamoto has since increased to 5.5 kilometers(see above). The "Jonstonarchive" estimates that the moon has asemi-major axis of 31 kilometers.[4]
Thisminor planet was named in honor of Japanese astronomerMasayuki Iwamoto (born 1954), adiscoverer of minor planets at the Tokushima Observatory (872).[2] The approved naming citation was published by theMinor Planet Center on 5 March 1996 (M.P.C. 26763).[11]
