1796 Riga

1796 Riga, provisional designation 1966 KB, is a dark asteroid from the outer region of the asteroid belt, approximately 70 kilometers in diameter. It was discovered on 16 May 1966, by Russian astronomer Nikolai Chernykh at the Crimean Astrophysical Observatory in Nauchnyj, on the Crimean peninsula.[15] It is named after the Latvian capital Riga.[2]

1796 Riga
Discovery [1]
Discovered byN. Chernykh
Discovery siteCrimean Astrophysical Obs.
Discovery date16 May 1966
Designations
(1796) Riga
Named after
Riga (capital city)[2]
1966 KB · 1935 GE
1941 FC1 · 1947 GA
1950 TF2 · 1953 GW
1960 JA · A907 TG
A907 UD
main-belt · (outer)[1]
Orbital characteristics [1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc66.06 yr (24,129 days)
Aphelion3.5474 AU
Perihelion3.1668 AU
3.3571 AU
Eccentricity0.0567
6.15 yr (2,247 days)
142.11°
0° 9m 36.72s / day
Inclination22.585°
186.73°
25.620°
Physical characteristics
Dimensions66.2±6.6 km[3]
68.089±1.037 km[4]
68.167±0.298 km[5]
71±7 km[6]
73.83±1.8 km[7]
85.79±1.57 km[8]
10.608±0.002 h[9][lower-alpha 1]
11.0±0.01 h[10]
16 h[11]
22.226±0.001 h[12]
0.028±0.001[8]
0.0376±0.002[7]
0.04±0.01[6]
0.044±0.005[5]
0.0442±0.0082[4]
0.05±0.01[3]
XFCU (Tholen)[1]
Cb (SMASS)[1]
P [4] · C [13][14]
B–V = 0.676[1]
U–B = 0.289[1]
9.59±0.40[14] · 9.84 (IRAS:12)[1][7] · 9.84[3][4][6][8][13]

    Orbit and classification

    The asteroid orbits the Sun in the outer main-belt at a distance of 3.2–3.5 AU once every 6 years and 2 months (2,247 days). Its orbit has an eccentricity of 0.06 and an inclination of 23° with respect to the ecliptic.[1] The body was first identified as "1907 TG" at the U.S Taunton Observatory (803) in 1907, and its first used precovery was taken at the Goethe Link Observatory in 1953, extending the asteroid's observation arc by 13 years prior to its official discovery observation.[15]

    Spectral type

    The carbonaceous C-type asteroid is also classified as a very dark and featureless reddish P-type body by the NEOWISE survey of the Wide-field Infrared Survey Explorer (WISE).[4][13][14] In the Tholen and SMASS taxonomy, it has a XFCU and Cb subtype, respectively.[1]

    Diameter and albedo

    According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the Japanese Akari satellite and NASA's WISE/NEOWISE mission, the asteroid measures between 66.2 and 85.7 kilometers in diameter and its surface has an albedo between 0.028 and 0.05.[3][4][5][6][7][8] The Collaborative Asteroid Lightcurve Link (CALL) agrees with the results obtained by IRAS, adopting a diameter of 73.83 kilometers with an albedo of 0.0376, based on an absolute magnitude of 9.84.[13]

    Rotation period

    Several rotational lightcurve for this asteroid were obtained from photometric observations since 1997. They gave a variety of rotation periods from 10.608 to 22.226 hours with inconsistent brightness variations in the range of 0.05 to 0.40 magnitude (U=2/2-/n.a./2).[9][10][11][12][lower-alpha 1] CALL adopts the results of the most observations made by astronomer Julian Oey at the Australian Blue Mountains Observatory (Q68) in March 2014, which gave a period of 22.226±0.001 hours and an amplitude of 0.40±0.05 magnitude (U=2).[12][13]

    Naming

    The minor planet was named after Riga, the capital of Latvia and location of the Astronomical Observatory of the University of Latvia. The name was proposed by Matiss A. Dirikis, who was a member of the observatory at the Latvian State University, and after whom the asteroid 1805 Dirikis is named.[2] The official naming citation was published by the Minor Planet Center on 25 September 1971 (M.P.C. 3185).[16]

    Notes
    1. Lightcurve plot of 1796 Riga, Palmer Divide Observatory, by B. D. Warner (2003), with a rotation period 10.608±0.002 hours and a brightness amplitude of 0.14±0.02 mag. Summary figures at Collaborative Asteroid Lightcurve Link (CALL)

    References
    1. "JPL Small-Body Database Browser: 1796 Riga (1966 KB)" (2016-11-04 last obs.). Jet Propulsion Laboratory. Retrieved 1 July 2017.
    2. Schmadel, Lutz D. (2007). "(1796) Riga". Dictionary of Minor Planet Names – (1796) Riga. Springer Berlin Heidelberg. p. 144. doi:10.1007/978-3-540-29925-7_1797. ISBN 978-3-540-00238-3.
    3. Alí-Lagoa, V.; Licandro, J.; Gil-Hutton, R.; Cañ; ada-Assandri, M.; Delbo', M.; et al. (June 2016). "Differences between the Pallas collisional family and similarly sized B-type asteroids". Astronomy and Astrophysics. 591: 11. Bibcode:2016A&A...591A..14A. doi:10.1051/0004-6361/201527660. Retrieved 10 August 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.; 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. Retrieved 29 October 2016.
    6. Alí-Lagoa, V.; de León, J.; Licandro, J.; Delbó, M.; Campins, H.; Pinilla-Alonso, N.; et al. (June 2013). "Physical properties of B-type asteroids from WISE data". Astronomy and Astrophysics. 554: 16. arXiv:1303.5487. Bibcode:2013A&A...554A..71A. doi:10.1051/0004-6361/201220680. Retrieved 29 October 2016.
    7. Tedesco, E. F.; Noah, P. V.; Noah, M.; Price, S. D. (October 2004). "IRAS Minor Planet Survey V6.0". NASA Planetary Data System – IRAS-A-FPA-3-RDR-IMPS-V6.0. Bibcode:2004PDSS...12.....T. Retrieved 17 October 2019.
    8. 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)
    9. Warner, Brian D. (April 2011). "Upon Further Review: VI. An Examination of Previous Lightcurve Analysis from the Palmer Divide Observatory". The Minor Planet Bulletin. 38 (2): 96–101. Bibcode:2011MPBu...38...96W. ISSN 1052-8091. Retrieved 17 November 2015.
    10. Warner, Brian D. (March 2004). "Rotation rates for asteroids 875, 926, 1679, 1796, 3915, 4209, and 34817". The Minor Planet Bulletin. 31 (1): 19–22. Bibcode:2004MPBu...31...19W. ISSN 1052-8091. Retrieved 17 November 2015.
    11. Chiorny, V. G.; Shevchenko, V. G.; Krugly, Yu. N.; Velichko, F. P.; Gaftonyuk, N. M. (May 2007). "Photometry of asteroids: Lightcurves of 24 asteroids obtained in 1993 2005". Planetary and Space Science. 55 (7–8): 986–997. Bibcode:2007P&SS...55..986C. doi:10.1016/j.pss.2007.01.001. Retrieved 17 November 2015.
    12. Oey, Julian (January 2016). "Lightcurve Analysis of Asteroids from Blue Mountains Observatory in 2014". The Minor Planet Bulletin. 43 (1): 45–51. Bibcode:2016MPBu...43...45O. ISSN 1052-8091. Retrieved 29 October 2016.
    13. "LCDB Data for (1796) Riga". Asteroid Lightcurve Database (LCDB). Retrieved 29 October 2016.
    14. 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 29 October 2016.
    15. "1796 Riga (1966 KB)". Minor Planet Center. Retrieved 29 October 2016.
    16. Schmadel, Lutz D. "Appendix – Publication Dates of the MPCs". Dictionary of Minor Planet Names – Addendum to Fifth Edition (2006–2008). Springer Berlin Heidelberg. p. 221. doi:10.1007/978-3-642-01965-4. ISBN 978-3-642-01964-7.

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