| 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 | 80.17yr (29,283 d) |
| Aphelion | 2.2851AU |
| 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] | |
1990 Pilcher, provisional designation1956 EE, is a stony backgroundasteroid from the Florian region of the innerasteroid belt, approximately 7 kilometers (4.3 miles) in diameter. It was discovered on 9 March 1956, by German astronomerKarl Reinmuth at theHeidelberg-Königstuhl State Observatory in Heidelberg, Germany. In 1982, it was named by theMPC for American physicist and photometristFrederick Pilcher.[1] TheS-type asteroid has a shortrotation period of 2.8 hours.[5]
Pilcher is a non-family asteroid of the main belt'sbackground population when applying thehierarchical clustering method (HCM) to itsproper orbital elements (Nesvorný, Milani and Knežević).[3][4] In a previous HCM-analysis (Zappalà) and based on osculating Keplerianorbital elements, the asteroid has also been classified as a member of theFlora family (402), a giantasteroid family and the largest family of stony asteroids in the main-belt.[5][6]
It orbits the Sun in the Florian region of theinner 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 aneccentricity of 0.05 and aninclination of 3° with respect to theecliptic.[2]
The asteroid was first observed as1937 JL atNice Observatory in May 1937. The body'sobservation arc begins with aprecovery taken atPalomar Observatory in June 1950, or six years prior to its official discovery observation at Heidelberg.[1]
In theTholen classification,Pilcher is a common, stonyS-type asteroid.[2]
In March 2017, a first rotationallightcurve ofPilcher was obtained from photometric observations at theFlarestar Observatory on the island of Malta. Lightcurve analysis gave a shortrotation period of 2.842 hours with a brightness amplitude of 0.10magnitude, indicative for a rather spherical shape (U=2+).[9]
According to the survey carried out by theNEOWISE mission of NASA'sWide-field Infrared Survey Explorer,Pilcher measures between 6.754 and 7.273 kilometers in diameter and its surface has analbedo between 0.1864 and 0.215.[7][8]
TheCollaborative Asteroid Lightcurve Link assumes an albedo of 0.24 – derived from8 Flora, the Flora family'sparent body and namesake – and calculates a diameter of 6.39 kilometers based on anabsolute magnitude of 13.14.[5]
Thisminor planet was named after American astronomerFrederick Pilcher, a retired professor of Physics atIllinois College and prolific lightcurve photometrist at his Organ Mesa Observatory (G50) in New Mexico.[1] The official naming citation was published by theMinor Planet Center on 8 April 1982 (M.P.C. 6833).[10]
