| Discovery[1] | |
|---|---|
| Discovered by | M. F. Wolf |
| Discovery site | Heidelberg Obs. |
| Discovery date | 13 March 1931 |
| Designations | |
| (1178) Irmela | |
Named after | Irmela Ruska (wife ofErnst Ruska)[2] |
| 1931 EC · 1940 GC 1962 JD · 1988 CK6 | |
| main-belt · (middle)[3] | |
| Orbital characteristics[1] | |
| Epoch 16 February 2017 (JD 2457800.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 85.83 yr (31,351 days) |
| Aphelion | 3.1700AU |
| Perihelion | 2.1916 AU |
| 2.6808 AU | |
| Eccentricity | 0.1825 |
| 4.39yr (1,603 days) | |
| 209.87° | |
| 0° 13m 28.56s / day | |
| Inclination | 6.9511° |
| 170.11° | |
| 357.21° | |
| Physical characteristics | |
| Dimensions | 17.00±3.43 km[4] 17.50±4.91 km[5] 17.90±0.57 km[6] 19.05 km(derived)[3] 19.09±0.8 km(IRAS:15)[7] 19.663±0.049 km[8] 20.683±0.181 km[9] |
| 11.989±0.001 h[10] 19.17h[11] | |
| 0.0503±0.0031[9] 0.070±0.006[8] 0.08±0.03[4] 0.08±0.07[5] 0.0838(derived)[3] 0.0916±0.008(IRAS:15)[7] 0.105±0.007[6] | |
| S[3] | |
| 11.81[1][4][6][7] · 11.87±0.35[12] · 11.91[3][9][11] · 12.14[5] | |
1178 Irmela, provisional designation1931 EC, is a stonyasteroid from the middle regions of theasteroid belt, approximately 19 kilometers in diameter.
It was discovered on 13 March 1931, by German astronomerMax Wolf atHeidelberg Observatory in southwest Germany.[13] The asteroid was named after Irmela Ruska, wife ofErnst Ruska.[2]
Irmela orbits the Sun in thecentral main-belt at a distance of 2.2–3.2 AU once every 4 years and 5 months (1,603 days). Its orbit has aneccentricity of 0.18 and aninclination of 7° with respect to theecliptic.[1]A firstprecovery was taken atLowell Observatory in February 1931, extending the body'sobservation arc by 3 weeks prior to its official discovery observation at Heidelberg.[13]
In May 1984, a first rotationallightcurve ofIrmela was obtained from photometric observations by American astronomerRichard Binzel. Lightcurve analysis gave arotation period of 19.17 hours with a brightness variation of 0.34magnitude (U=2).[11]
In March 2010, astronomerRobert Stephens obtained another lightcurve at the Center for Solar System Studies, that gave a divergent period of 11.989 hours with an amplitude of 0.40 magnitude (U=2).[10]
According to the surveys carried out by the Infrared Astronomical SatelliteIRAS, the JapaneseAkari satellite, and NASA'sWide-field Infrared Survey Explorer with its subsequentNEOWISE mission,Irmela measures between 17.00 and 20.683 kilometers in diameter and its surface has analbedo between 0.0503 and 0.105.[4][5][6][7][8][9]
10μm radiometric data collected fromKitt Peak National Observatory in 1975, gave a diameter estimate of 19 kilometers.[14]
TheCollaborative Asteroid Lightcurve Link characterizesIrmela as a commonS-type asteroid, derives an albedo of 0.0838 and calculates a diameter of 19.05 kilometers with anabsolute magnitude of 11.91.[3]
Thisminor planet was named after Irmela Ruska, wife of the inventor of the electron microscope and 1986 Nobelist, the German physicistErnst Ruska (1906–1988), who shared the Nobel prize withGerd Binnig andHeinrich Rohrer. The naming was granted by Max Wolf to his colleagueAugust Kopff, himself a prolificdiscoverer of minor planets. The citation was published byPaul Herget inThe Names of the Minor Planets (H 109).[2]
