784 Pickeringia

784 Pickeringia (prov. designation: A914 FC or 1914 UM) is a large background asteroid, approximately 76 kilometers (47 miles) in diameter, located in the outer region of the asteroid belt. It was discovered on 20 March 1914, by American astronomer Joel Hastings Metcalf at the Winchester Observatory (799) in Massachusetts.[1] The dark C-type asteroid has a rotation period of 13.1 hours and an irregular shape. It was named after American astronomers Edward Charles Pickering (1846–1919) and his brother William Henry Pickering (1858–1938).[2]

784 Pickeringia
Shape of Pickeringia from modeled lightcurve
Discovery [1]
Discovered byJ. H. Metcalf
Discovery siteWinchester Obs. (799)
Discovery date20 March 1914
Designations
(784) Pickeringia
Named after
A914 FC · 1914 UM
Orbital characteristics [3]
Epoch 31 May 2020 (JD 2459000.5)
Uncertainty parameter 0
Observation arc105.82 yr (38,652 d)
Aphelion3.8458 AU
Perihelion2.3455 AU
3.0956 AU
Eccentricity0.2423
5.45 yr (1,989 d)
97.354°
0° 10m 51.6s / day
Inclination12.284°
14.917°
238.01°
Physical characteristics
Mean diameter
  • 74.89±0.92 km[7]
  • 75.596±0.311 km[8]
  • 89.42±3.4 km[9]
Mass(3.74±0.32)×1018 kg[10]
Mean density
12.70±3.49 g/cm3[10]
13.144±0.005 h[11]
  • 0.0555±0.005[9]
  • 0.080±0.002[7]
  • 0.086±0.014[8]

    Orbit and classification

    Pickeringia is a non-family asteroid of the main belt's background population when applying the hierarchical clustering method to its proper orbital elements.[4][5][6] It orbits the Sun in the outer asteroid belt at a distance of 2.3–3.8 AU once every 5 years and 5 months (1,989 days; semi-major axis of 3.1 AU). Its orbit has an eccentricity of 0.24 and an inclination of 12° with respect to the ecliptic.[3] The body's observation arc begins at Heidelberg Observatory on 30 September 1921, more than seven years after its official discovery observation at Winchester Observatory (799).[1]

    Naming

    This minor planet was named after American astronomers Edward Charles Pickering (1846–1919) and his brother William Henry Pickering (1858–1938), who were the directors of the Harvard Observatory and the Boyden Station at Arequipa, respectively. William Henry also discovered Phoebe, an irregular moon of Saturn. The naming was mentioned in The Names of the Minor Planets by Paul Herget in 1955 (H 78).[2] The lunar crater Pickering and the Martian crater Pickering were also named in honor of the two astronomers.[13][14]

    Physical characteristics

    In the Bus–Binzel SMASS classification, Pickeringia is a common, carbonaceous C-type asteroid.[3]

    Rotation period

    In January 2017, a rotational lightcurve of Pickeringia was obtained from photometric observations by the Spanish group of asteroids observers (OBAS). Lightcurve analysis gave a rotation period of 13.144±0.005 hours with a brightness variation of 0.17±0.03 magnitude (U=2+).[11]

    The result supersedes observations taken during the 1990s by European astronomers using the ESO 0.5-metre telescope at La Silla Observatory, Chile, which gave a period of 13 hours with an amplitude of 0.40 magnitude (U=2).[15] as well as a period determination by French amateur astronomer Laurent Bernasconi in December 2004, which gave 13.17±0.05 h and an amplitude of 0.20±0.01 magnitude (U=2).[16]

    Modeled lightcurve

    Two modeled lightcurves, published by Josef Ďurech and Josef Hanuš in 2016, using photometric data from the Lowell Photometric Database (LPD) and other sources, gave a sidereal period of 13.16995±0.00001 and 13.16998±0.00005, respectively. Each modeled lightcurve also determined two spin axes of (99.0°, 67.0°) and (283.0°, 30.0°), as well as (282.0°, 35.0°) and (103.0°, 68.0°) in ecliptic coordinates (λ, β), respectively.[17][18] The online version of the Database of Asteroid Models from Inversion Techniques gives two poles at (103°, 68.0°) and (282°, 35.0°) with a nearly identical sidereal period.[lower-alpha 1]

    Diameter and albedo

    According to the surveys carried out by the Japanese Akari satellite, the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer (WISE), and the Infrared Astronomical Satellite IRAS, Pickeringia measures (74.89±0.92), (75.596±0.311) and (89.42±3.4) kilometers in diameter and its surface has an albedo of (0.080±0.002), (0.086±0.014) and (0.0555±0.005), respectively.[7][8][9] The Collaborative Asteroid Lightcurve Link derives an albedo of 0.0423 and a diameter of 89.19 kilometers based on an absolute magnitude of 9.3.[19] while Carry gives a diameter of 82.52±7.18 km and estimates a mass of (3.74±0.32)×1018 kilogram from an unrealistic density of 12.70±3.49 g/cm3.[10] Alternative mean-diameter measurements published by the WISE team include (70.14±18.05 km), (89.13±13.47 km) and (89.673±1.178 km) with corresponding albedos of (0.049±0.348), (0.0552±0.0109) and (0.06±0.02).[5][19] On 7 August 2008, an asteroid occultation of Pickeringia gave a best-fit ellipse dimension of (89.0 km × 89.0 km), with a poor quality rating of 1. These timed observations are taken when the asteroid passes in front of a distant star.[5]

    Notes
    1. DAMIT-Online: Poles for (784) Pickeringia, with (103°, 68.0°) (λ1/β1) and (282°, 35.0°) (λ2/β2) in ecliptic coordinates. Summary figures and shape models at the Database of Asteroid Models from Inversion Techniques (DAMIT).

    References
    1. "784 Pickeringia (A914 FC)". Minor Planet Center. Retrieved 31 March 2020.
    2. Schmadel, Lutz D. (2007). "(784) Pickeringia". Dictionary of Minor Planet Names. Springer Berlin Heidelberg. p. 74. doi:10.1007/978-3-540-29925-7_785. ISBN 978-3-540-00238-3.
    3. "JPL Small-Body Database Browser: 784 Pickeringia (A914 FC)" (2020-01-24 last obs.). Jet Propulsion Laboratory. Retrieved 31 March 2020.
    4. "Asteroid 784 Pickeringia – Proper Elements". AstDyS-2, Asteroids – Dynamic Site. Retrieved 31 March 2020.
    5. "Asteroid 784 Pickeringia". Small Bodies Data Ferret. Retrieved 31 March 2020.
    6. Zappalà, V.; Bendjoya, Ph.; Cellino, A.; Farinella, P.; Froeschle, C. (1997). "Asteroid Dynamical Families". NASA Planetary Data System: EAR-A-5-DDR-FAMILY-V4.1. Retrieved 31 March 2020. (PDS main page)
    7. Usui, Fumihiko; Kuroda, Daisuke; Müller, Thomas G.; Hasegawa, Sunao; Ishiguro, Masateru; Ootsubo, Takafumi; et al. (October 2011). "Asteroid Catalog Using Akari: AKARI/IRC Mid-Infrared Asteroid Survey". Publications of the Astronomical Society of Japan. 63 (5): 1117–1138. Bibcode:2011PASJ...63.1117U. doi:10.1093/pasj/63.5.1117. Retrieved 31 March 2020. (online, AcuA catalog p. 153)
    8. Mainzer, A. K.; Bauer, J. M.; Cutri, R. M.; Grav, T.; Kramer, E. A.; Masiero, J. R.; et al. (June 2016). "NEOWISE Diameters and Albedos V1.0". NASA Planetary Data System. Bibcode:2016PDSS..247.....M. Retrieved 31 March 2020.
    9. Tedesco, E. F.; Noah, P. V.; Noah, M.; Price, S. D. (October 2004). "IRAS Minor Planet Survey V6.0". NASA Planetary Data System. 12: IRAS-A-FPA-3-RDR-IMPS-V6.0. Bibcode:2004PDSS...12.....T. Retrieved 31 March 2020.
    10. Carry, B. (December 2012). "Density of asteroids". Planetary and Space Science. 73 (1): 98–118. arXiv:1203.4336. Bibcode:2012P&SS...73...98C. doi:10.1016/j.pss.2012.03.009. ISSN 0032-0633. See Table 1.
    11. Mas, Vicente; Fornas, G.; Lozano, Juan; Rodrigo, Onofre; Fornas, A.; Carreño, A.; et al. (January 2018). "Twenty-one Asteroid Lightcurves at Asteroids Observers (OBAS) - MPPD: Nov 2016 - May 2017" (PDF). Minor Planet Bulletin. 45 (1): 76–82. Bibcode:2018MPBu...45...76M. ISSN 1052-8091. Retrieved 31 March 2020.
    12. Warner, Brian D. (December 2007). "Initial Results of a Dedicated H-G Project" (PDF). Minor Planet Bulletin. 34 (4): 113–119. Bibcode:2007MPBu...34..113W. ISSN 1052-8091. Retrieved 31 March 2020.
    13. "Lunar crater Pickering". Gazetteer of Planetary Nomenclature. USGS Astrogeology Research Program.
    14. "Martian crater Pickering". Gazetteer of Planetary Nomenclature. USGS Astrogeology Research Program.
    15. Hainaut-Rouelle, M. -C.; Hainaut, O. R.; Detal, A. (July 1995). "Lightcurves of selected minor planets". Astronomy and Astrophysics Supplement Series. 112: 125. Bibcode:1995A&AS..112..125H. ISSN 0365-0138.
    16. Behrend, Raoul. "Asteroids and comets rotation curves – (784) Pickeringia". Geneva Observatory. Retrieved 31 March 2020.
    17. Ďurech, J.; Hanuš, J.; Oszkiewicz, D.; Vančo, R. (March 2016). "Asteroid models from the Lowell photometric database". Astronomy and Astrophysics. 587: A48. arXiv:1601.02909. Bibcode:2016A&A...587A..48D. doi:10.1051/0004-6361/201527573. ISSN 0004-6361.
    18. Hanuš, J.; Ďurech, J.; Oszkiewicz, D. A.; Behrend, R.; Carry, B.; Delbo, M.; et al. (February 2016). "New and updated convex shape models of asteroids based on optical data from a large collaboration network". Astronomy and Astrophysics. 586: A108. arXiv:1510.07422. Bibcode:2016A&A...586A.108H. doi:10.1051/0004-6361/201527441. ISSN 0004-6361.
    19. "LCDB Data for (784) Pickeringia". Asteroid Lightcurve Database (LCDB). Retrieved 31 March 2020.
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