1990 Pilcher
Stony background asteroid
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1990 Pilcher, provisional designation 1956 EE, is a stony background asteroid from the Florian region of the inner asteroid belt, approximately 7 kilometers (4.3 miles) in diameter. It was discovered on 9 March 1956, by German astronomer Karl Reinmuth at the Heidelberg-Königstuhl State Observatory in Heidelberg, Germany. In 1982, it was named by the MPC for American physicist and photometrist Frederick Pilcher.[1] The S-type asteroid has a short rotation period of 2.8 hours.[5]
| Discovery[1] | |
|---|---|
| Discovered by | K. Reinmuth |
| Discovery site | Heidelberg Obs. |
| Discovery date | 9 March 1956 |
| Designations | |
| (1990) Pilcher | |
Named after | Frederick Pilcher[1] (American photometrist) |
| 1956 EE · 1937 JL 1940 FA · 1959 CE1 1964 VS2 · 1972 EC 1972 GO · 1973 QM | |
| main-belt[1][2] · (inner) background[3][4] · Flora[5][6] | |
| Orbital characteristics[2] | |
| Epoch 23 March 2018 (JD 2458200.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 80.17 yr (29,283 d) |
| Aphelion | 2.2851 AU |
| Perihelion | 2.0625 AU |
| 2.1738 AU | |
| Eccentricity | 0.0512 |
| 3.21 yr (1,171 d) | |
| 92.884° | |
| 0° 18m 27s / day | |
| Inclination | 3.1320° |
| 193.63° | |
| 11.957° | |
| Physical characteristics | |
| 6.39 km (calculated)[5] 6.754±0.167 km[7] 7.273±0.064 km[8] | |
| 2.842±0.001 h[9] | |
| 0.1864±0.0254[8] 0.215±0.039[7] 0.24 (assumed)[5] | |
| Tholen = S[2] S (assumed)[5] B–V = 0.850[2] U–B = 0.504[2] | |
| 13.14[2][5][8] | |
Orbit and classification
Pilcher is a non-family asteroid of the main belt's background population when applying the hierarchical clustering method (HCM) to its proper orbital elements (Nesvorný, Milani and Knežević).[3][4] In a previous HCM-analysis (Zappalà) and based on osculating Keplerian orbital elements, the asteroid has also been classified as a member of the Flora family (402), a giant asteroid family and the largest family of stony asteroids in the main-belt.[5][6]
It orbits the Sun in the Florian region of the inner asteroid belt at a distance of 2.1–2.3 AU once every 3 years and 3 months (1,171 days; semi-major axis of 2.17 AU). Its orbit has an eccentricity of 0.05 and an inclination of 3° with respect to the ecliptic.[2]
The asteroid was first observed as 1937 JL at Nice Observatory in May 1937. The body's observation arc begins with a precovery taken at Palomar Observatory in June 1950, or six years prior to its official discovery observation at Heidelberg.[1]
Physical characteristics
In the Tholen classification, Pilcher is a common, stony S-type asteroid.[2]
Rotation period
In March 2017, a first rotational lightcurve of Pilcher was obtained from photometric observations at the Flarestar Observatory on the island of Malta. Lightcurve analysis gave a short rotation period of 2.842 hours with a brightness amplitude of 0.10 magnitude, indicative for a rather spherical shape (U=2+).[9]
Diameter and albedo
According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Pilcher measures between 6.754 and 7.273 kilometers in diameter and its surface has an albedo between 0.1864 and 0.215.[7][8]
The Collaborative Asteroid Lightcurve Link assumes an albedo of 0.24 – derived from 8 Flora, the Flora family's parent body and namesake – and calculates a diameter of 6.39 kilometers based on an absolute magnitude of 13.14.[5]
Naming
This minor planet was named after American astronomer Frederick Pilcher, a retired professor of Physics at Illinois College and prolific lightcurve photometrist at his Organ Mesa Observatory (G50) in New Mexico.[1] The official naming citation was published by the Minor Planet Center on 8 April 1982 (M.P.C. 6833).[10]
