2187 La Silla

2187 La Silla, provisionally designated 1976 UH, is a stony Eunomia asteroid from the middle region of the asteroid belt, approximately 12 kilometers in diameter.

2187 La Silla
Discovery [1]
Discovered byR. M. West
Discovery siteLa Silla Obs.
Discovery date24 October 1976
Designations
(2187) La Silla
Named after
La Silla Observatory
(observatory and mountain)[2]
1976 UH
main-belt · Eunomia[3]
Orbital characteristics [1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc40.42 yr (14,764 days)
Aphelion2.8354 AU
Perihelion2.2352 AU
2.5353 AU
Eccentricity0.1184
4.04 yr (1,474 days)
139.36°
0° 14m 39.12s / day
Inclination13.261°
137.27°
214.21°
Physical characteristics
Dimensions6.64 km (calculated)[3]
12.320±0.093 km[4][5]
12.96±0.70 km[6]
11.8431±0.0049 h[7]
16 h[8]
0.054±0.004[4][5]
0.080±0.010[6]
0.21 (assumed)[3]
S [3]
13.00[4][6] · 13.2[1][3] · 13.21±0.38[9] · 13.307±0.005 (R)[7]

    It was discovered on 24 October 1976 by Danish astronomer Richard Martin West at ESO's La Silla site in northern Chile, and named after the discovering observatory and the mountain it is located on.[2][10]

    Classification and orbit

    La Silla is a member of the Eunomia family, a large collisional group of S-type asteroids and the most prominent family in the intermediate main-belt. It orbits the Sun in the central main-belt at a distance of 2.2–2.8 AU once every 4.04 years (1,474 days). Its orbit has an eccentricity of 0.12 and an inclination of 13° with respect to the ecliptic.[1] La Silla's observation arc begins with its discovery observation in 1976, as no precoveries were taken, and no previous identifications were made.[10]

    Physical characteristics

    In July 2007, French amateur astronomer René Roy obtained a rotational lightcurve from photometric observations, giving a rotation period of 16 hours with a brightness variation of 0.6 magnitude (U=2-).[8] In March 2010, photometric observations at the Palomar Transient Factory gave a shorter period of 11.843 hours with an amplitude of 0.35 magnitude (U=2).[7]

    According to the space-based survey carried out by the Japanese Akari satellite and NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, La Silla measures 12.32 and 12.96 kilometers in diameter, and its surface has an albedo of 0.054 and 0.08, respectively.[4][5][6] The Collaborative Asteroid Lightcurve Link assumes an albedo of 0.21 – derived from 15 Eunomia, the family's largest member and namesake – and calculates a diameter of 6.64 kilometers.[3]

    Naming

    This minor planet is named after the site where ESO's discovering La Silla Observatory is situated. La Silla is a 2400-metre mountain on the outskirts of the Atacama desert, north of the city of La Serena in northern Chile.[2][11] The official naming citation was published by the Minor Planet Center on 1 December 1979 (M.P.C. 5039).[12]

    References
    1. "JPL Small-Body Database Browser: 2187 La Silla (1976 UH)" (2017-03-27 last obs.). Jet Propulsion Laboratory. Retrieved 12 June 2017.
    2. Schmadel, Lutz D. (2007). "(2187) la Silla". Dictionary of Minor Planet Names – (2187) La Silla. Springer Berlin Heidelberg. p. 178. doi:10.1007/978-3-540-29925-7_2188. ISBN 978-3-540-00238-3.
    3. "LCDB Data for (2187) La Silla". Asteroid Lightcurve Database (LCDB). Retrieved 13 December 2016.
    4. 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.
    5. Masiero, Joseph R.; Mainzer, A. K.; Grav, T.; Bauer, J. M.; Cutri, R. M.; Dailey, J.; et al. (November 2011). "Main Belt Asteroids with WISE/NEOWISE. I. Preliminary Albedos and Diameters". The Astrophysical Journal. 741 (2): 20. arXiv:1109.4096. Bibcode:2011ApJ...741...68M. doi:10.1088/0004-637X/741/2/68. Retrieved 13 December 2016.
    6. 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 17 October 2019. (online, AcuA catalog p. 153)
    7. Waszczak, Adam; Chang, Chan-Kao; Ofek, Eran O.; Laher, Russ; Masci, Frank; Levitan, David; et al. (September 2015). "Asteroid Light Curves from the Palomar Transient Factory Survey: Rotation Periods and Phase Functions from Sparse Photometry". The Astronomical Journal. 150 (3): 35. arXiv:1504.04041. Bibcode:2015AJ....150...75W. doi:10.1088/0004-6256/150/3/75. Retrieved 13 December 2016.
    8. Behrend, Raoul. "Asteroids and comets rotation curves – (2187) La Silla". Geneva Observatory. Retrieved 13 December 2016.
    9. Veres, Peter; Jedicke, Robert; Fitzsimmons, Alan; Denneau, Larry; Granvik, Mikael; Bolin, Bryce; et al. (November 2015). "Absolute magnitudes and slope parameters for 250,000 asteroids observed by Pan-STARRS PS1 - Preliminary results". Icarus. 261: 34–47. arXiv:1506.00762. Bibcode:2015Icar..261...34V. doi:10.1016/j.icarus.2015.08.007. Retrieved 13 December 2016.
    10. "2187 La Silla (1976 UH)". Minor Planet Center. Retrieved 13 December 2016.
    11. "About La Silla – General Information". ESO – European Southern Observatory. Retrieved 4 April 2017.
    12. "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 13 December 2016.

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