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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. The S-type asteroid has a short rotation period of 2.8 hours.

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). 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.

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.

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.

Physical characteristics

In the Tholen classification, Pilcher is a common, stony S-type asteroid.

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+).

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.

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.

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. The official naming citation was published by the Minor Planet Center on 8 April 1982 (M.P.C. 6833).

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.

External links

• Minor Planet Lightcurve Data (Frederick Pilcher), Astronomical Society of Las Cruces (ASLC)
• Asteroid Lightcurve Database (LCDB), query form (info Archived 16 December 2017 at the Wayback Machine)
• Dictionary of Minor Planet Names, Google books
• Discovery Circumstances: Numbered Minor Planets (1)-(5000) – Minor Planet Center
• 1990 Pilcher at AstDyS-2, Asteroids—Dynamic Site
  • Ephemeris · Observation prediction · Orbital info · Proper elements · Observational info
• 1990 Pilcher at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit viewer · Orbit parameters · Physical parameters

• Minor planet object articles (numbered)
• Background asteroids
• Discoveries by Karl Wilhelm Reinmuth
• Named minor planets
• S-type asteroids (Tholen)
• Astronomical objects discovered in 1956