| Discovery[1] | |
|---|---|
| Discovered by | P. Wild |
| Discovery site | Zimmerwald Obs. |
| Discovery date | 30 October 1972 |
| Designations | |
| (1845) Helewalda | |
Named after | Helen Gachnang (friend of discoverer)[2] |
| 1972 UC · 1931 VC1 1954 GG · 1971 OR 1971 QX2 | |
| main-belt · (outer)[3] Eos[4] | |
| Orbital characteristics[1] | |
| Epoch 4 September 2017 (JD 2458000.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 85.50 yr (31,229 days) |
| Aphelion | 3.1371AU |
| Perihelion | 2.8001 AU |
| 2.9686 AU | |
| Eccentricity | 0.0568 |
| 5.11yr (1,868 days) | |
| 210.23° | |
| 0° 11m 33.72s / day | |
| Inclination | 10.720° |
| 142.61° | |
| 325.05° | |
| Physical characteristics | |
| Dimensions | 19.930±0.377[5] 20.426±0.147 km[6] 32.03 km(calculated)[3] |
| 7.2786±0.0002h[7] 7.3985±0.0098 h[8] 7.399±0.004 h[9] 7.4±0.1 h[10] | |
| 0.057(assumed)[3] 0.1289±0.0185[6] 0.134±0.014[5] | |
| C(assumed)[3] | |
| 11.193±0.002[8] · 11.2[1][3] · 11.3[6] · 11.60±0.98[11] | |
1845 Helewalda (provisional designation1972 UC) is a carbonaceous Eoanasteroid in the outer regions of theasteroid belt, approximately 20 kilometers in diameter. It was discovered by Swiss astronomerPaul Wild atZimmerwald Observatory near Bern, Switzerland, on 30 October 1972.[12] The asteroid was named after Helen Gachnang, a friend of the discoverer.[2]
Helewalda is a member of theEos family (606), the largestasteroid family in theouter main belt consisting of nearly 10,000 asteroids.[4][13]: 23 It orbits the Sun in theouter main-belt at a distance of 2.8–3.1 AU once every 5 years and 1 month (1,868 days). Its orbit has aneccentricity of 0.06 and aninclination of 11° with respect to theecliptic.[1] The firstprecovery was taken atLowell Observatory in 1931, extending the asteroid'sobservation arc by 41 years prior to its discovery.[12]
Helewalda is an assumed carbonaceousC-type asteroid.[3]
Based on observations made by French astronomerRené Roy in March 2010, Helewalda has a well-determinedrotation period of7.2786±0.0002 hours with a brightness variation of 0.26 inmagnitude (U=3-).[7]
Between 2009 and 2015, otherlightcurves were obtained at the Oakley Southern Sky Observatory in Australia (E09), the Via Capote Observatory at Thousand Oaks, California (G69), and thePalomar Transient Factory at Palomar Observatory. They gave a similar period of7.399±0.004,7.4±0.1 and7.3985±0.0098 hours with a corresponding amplitude of 0.20, 0.28 and 0.15, respectively (U=2/2+/2).[9][10][8]
TheCollaborative Asteroid Lightcurve Link calculates a diameter of 32.0 kilometers, based on an assumed standard albedo for carbonaceousC-type asteroids of 0.057,[3] while theNEOWISE mission of NASA'sWide-field Infrared Survey Explorer measured a higher albedo of 0.134 and 0.129 and a corresponding diameter of 19.9 and 20.4 kilometers in diameter, respectively.[5][6]
The discoverer, Paul Wild, named a pair of asteroids after two of his former schoolmates, Susi and Helen, both from the small village ofWald, Zürich in Switzerland. This one was dedicated to Helen Gachnang, while the previously numbered asteroid1844 Susilva was given to Susi Petit-Pierre.[2][14] The officialnaming citation was published by theMinor Planet Center on 18 April 1977 (M.P.C. 4156).[15]
Helen Gachnang and Susi Petit-Pierre visit the Eschenberg Observatory
