1990 Pilcher

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]

1990 Pilcher
Discovery [1]
Discovered byK. Reinmuth
Discovery siteHeidelberg Obs.
Discovery date9 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 arc80.17 yr (29,283 d)
Aphelion2.2851 AU
Perihelion2.0625 AU
2.1738 AU
Eccentricity0.0512
3.21 yr (1,171 d)
92.884°
0° 18m 27s / day
Inclination3.1320°
193.63°
11.957°
Physical characteristics
Mean diameter
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]

    References
    1. "1990 Pilcher (1956 EE)". Minor Planet Center. Retrieved 20 March 2018.
    2. "JPL Small-Body Database Browser: 1990 Pilcher (1956 EE)" (2017-07-05 last obs.). Jet Propulsion Laboratory. Retrieved 20 March 2018.
    3. "Asteroid (1990) Pilcher". AstDyS-2, Asteroids – Dynamic Site. Retrieved 25 May 2018.
    4. "Small Bodies Data Ferret". Nesvorny HCM Asteroid Families V3.0. Archived from the original on 2 August 2017. Retrieved 30 May 2018.
    5. "LCDB Data for (1990) Pilcher". Asteroid Lightcurve Database (LCDB). Retrieved 20 March 2018.
    6. "Asteroid 1990 Pilcher". Small Bodies Data Ferret. Retrieved 30 May 2018.
    7. Masiero, Joseph R.; Grav, T.; Mainzer, A. K.; Nugent, C. R.; Bauer, J. M.; Stevenson, R.; et al. (August 2014). "Main-belt Asteroids with WISE/NEOWISE: Near-infrared Albedos". The Astrophysical Journal. 791 (2): 11. arXiv:1406.6645. Bibcode:2014ApJ...791..121M. doi:10.1088/0004-637X/791/2/121.
    8. Mainzer, A.; Grav, T.; Masiero, J.; Hand, E.; Bauer, J.; Tholen, D.; et al. (November 2011). "NEOWISE Studies of Spectrophotometrically Classified Asteroids: Preliminary Results". The Astrophysical Journal. 741 (2): 25. arXiv:1109.6407. Bibcode:2011ApJ...741...90M. doi:10.1088/0004-637X/741/2/90.
    9. Brincat, Stephen M.; Grech, Winston (October 2017). "Photometric Observations of Main-belt Asteroids 1990 Pilcher and 8443 Svecica". The Minor Planet Bulletin. 44 (4): 287–288. Bibcode:2017MPBu...44..287B. ISSN 1052-8091.
    10. "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 20 March 2018.

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