| Discovery[1] | |
|---|---|
| Discovered by | K. Reinmuth |
| Discovery site | Heidelberg Obs. |
| Discovery date | 15 February 1920 |
| Designations | |
| (926) Imhilde | |
Named after | Name picked from the almanac Lahrer Hinkender Bote[2] |
| A920 CB · 1920 GN 1931 GB · 1964 WB | |
| main-belt[1][3] · (outer) Imhilde[4] | |
| Orbital characteristics[3] | |
| Epoch 31 May 2020 (JD 2459000.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 99.70yr (36,416 d) |
| Aphelion | 3.5251AU |
| Perihelion | 2.4365 AU |
| 2.9808 AU | |
| Eccentricity | 0.1826 |
| 5.15 yr (1,880 d) | |
| 97.231° | |
| 0° 11m 29.4s / day | |
| Inclination | 16.325° |
| 48.971° | |
| 173.79° | |
| Physical characteristics | |
| 26.8±0.5 h[8][a] | |
| C(SDSS-MOC)[9] | |
| 10.5[1][3] | |
926 Imhilde (prov. designation:A920 CBor1920 GN) is a darkasteroid and the principal body and namesake of theImhilde family, located in the outer regions of theasteroid belt. It was discovered by astronomerKarl Reinmuth at theHeidelberg Observatory in southwest Germany on 15 February 1920.[1] The carbonaceousC-type asteroid has arotation period of 26.8 hours and measures approximately 48 kilometers (30 miles) in diameter. It was named "Imhilde", a common German female name unrelated to the discoverer's contemporaries, that was taken from the almanacLahrer Hinkender Bote.[2]
When applying the synthetichierarchical clustering method (HCM) byNesvorný,Imhilde is the principal body and namesake of theImhilde family (639), a smallasteroid cluster with only a few dozens members.[4][10]: 23 However, according to another HCM-analysis byMilani andKnežević (AstDys), it is abackground asteroid as the analysis does not recognize this family.[11]Imhilde orbits the Sun in theouter asteroid belt at a distance of 2.4–3.5 AU once every 5 years and 2 months (1,880 days;semi-major axis of 2.98 AU). Its orbit has aneccentricity of 0.18 and aninclination of 16° with respect to theecliptic.[3] The body'sobservation arc begins atHeidelberg Observatory on 17 February 1920, two nights after its official discovery observation.[1]
Thisminor planet was named "Imhilde", after a female name picked from theLahrer Hinkender Bote, published inLahr, southern Germany.[2] AHinkender Bote (lit. "limping messenger") was a very popularalmanac,[12] especially in thealemannic-speaking region from the late 17th throughout the early 20th century. Thecalendar section containsfeast days, the dates of important fairs andastronomical ephemerides. For 15 May, the calendar gives "Imhilde" as the Germanname day analogue next toSophie andTorquatus, the protestant and catholic entries in thecalendar of saints, likely referring toSophia of Rome andTorquatus of Acci.[13]
As with 22 other asteroids – starting with913 Otila, and ending with1144 Oda – Reinmuth selected names from this calendar due to his many asteroid discoveries that he had trouble thinking of proper names. These names are not related to the discoverer's contemporaries.Lutz Schmadel, the author of theDictionary of Minor Planet Names learned about Reinmuth's source of inspiration from private communications with Dutch astronomerIngrid van Houten-Groeneveld, who worked as a young astronomer at Heidelberg.[2]
In theSDSS-based taxonomy,Imhilde is a carbonaceousC-type asteroid.[9][14] The Imhilde family's overallspectral type is CX.[10]: 23
In April 2003, a rotationallightcurve ofImhilde was obtained fromphotometric observations byBrian Warner at thePalmer Divide Observatory (716) in Colorado. In 2011, after more than a decade of additional experience in asteroid lightcurve photometry, Warner reexamined the data set using improved tools and techniques. Lightcurve analysis gave arotation period of26.8±0.5 hours with a brightness variation of0.27±0.02magnitude (U=2).[8][a] Originally, the same data gave a period of26.1±0.5 hours with an amplitude0.2±0.02 magnitude (U=2).[15]
According to the survey carried out by theNEOWISE mission of NASA'sWide-field Infrared Survey Explorer (WISE), the Infrared Astronomical SatelliteIRAS, and the JapaneseAkari satellite,Imhilde measures (46.369±1.133), (48.48±1.1) and (49.87±0.92) kilometers in diameter and its surface has a lowalbedo of (0.052±0.007), (0.0570±0.003) and (0.054±0.002), respectively.[5][6][7]
TheCollaborative Asteroid Lightcurve Link derives an albedo of 0.0476 and a diameter of 48.39 km based on anabsolute magnitude of 10.5.[16] Further published mean-diameters and albedos by the WISE team include (44.148±10.193 km) and (46.37±1.13 km) and albedos of (0.055±0.020) and (0.052±0.007).[14][16] Anasteroid occultation observed on 8 November 2011, gave a best-fit ellipse dimension of 49.0 × 49.0 kilometers.[14] These timed observations are taken when the asteroid passes in front of a distant star. However the quality of the measurement is rated poorly.[14]
