917 Lyka

917 Lyka (prov. designation: A915 RR or 1915 S4) is a background asteroid, approximately 32 kilometers (20 miles) in diameter, located in the inner region of the asteroid belt. It was discovered on 5 September 1915, by Russian astronomer Grigory Neujmin at the Simeiz Observatory on the Crimean peninsula.[1] The X-type asteroid has a rotation period of 7.9 hours and is likely spherical in shape. It was named after Lyka, a friend of the discoverer's sister.[2]

917 Lyka
Discovery [1]
Discovered byG. Neujmin
Discovery siteSimeiz Obs.
Discovery date5 September 1915
Designations
(917) Lyka
Named after
Lyka, a friend of the discoverer's sister[2]
A915 RR · 1950 BS
1951 JJ · 1915 S4
1915 Σ4
main-belt [1][3] · (inner)
background [4][5]
Orbital characteristics [3]
Epoch 31 May 2020 (JD 2459000.5)
Uncertainty parameter 0
Observation arc100.18 yr (36,591 d)
Aphelion2.8590 AU
Perihelion1.9035 AU
2.3812 AU
Eccentricity0.2006
3.67 yr (1,342 d)
181.91°
0° 16m 5.52s / day
Inclination5.1264°
343.38°
359.90°
Physical characteristics
Mean diameter
  • 28.10±3.9 km[6]
  • 31.29±0.49 km[7]
  • 34.878±0.184 km[8]
7.867±0.006 h
  • 0.056±0.008[8]
  • 0.072±0.003[7]
  • 0.0891±0.031[6]
X (S3OS2)[9]
11.6[1][3]

    Orbit and classification

    Lyka 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] It orbits the Sun in the inner main-belt at a distance of 1.9–2.9 AU once every 3 years and 8 months (1,342 days; semi-major axis of 2.38 AU). Its orbit has an eccentricity of 0.20 and an inclination of 5° with respect to the ecliptic.[3] The body's observation arc begins at Simeiz on 1 September 1926, eleven years after to its official discovery observation.[1]

    Naming

    This minor planet was named after Lyka, a friend of the sister of discoverer Grigory Neujmin. Lutz Schmadel, the author of the Dictionary of Minor Planet Names learned about the meaning of the asteroid's name from private communications with long-time Simeiz astronomer Nikolai Chernykh.[2]

    Physical characteristics

    In both the Tholen- and SMASS-like taxonomy of the Small Solar System Objects Spectroscopic Survey (S3OS2), Lyka is an X-type asteroid.[5][9]

    Rotation period

    In January 2005, a rotational lightcurve of Lyka was obtained from photometric observations by Matthieu Conjat. Lightcurve analysis gave a well-defined rotation period of 7.867±0.006 hours with a low brightness variation of 0.17±0.02 magnitude, indicative of a rather spherical shape (U=3).[10] In October 2018, the period was confirmed by Laurent Bernasconi (7.8838±0.0003 h) and by Alfonso Carreño of OBAS (7.889±0.007 h) with amplitudes of 0.12±0.01 and 0.26±0.03, respectively (U=3/3).[10][11]

    Diameter and albedo

    According to the survey carried out by the Infrared Astronomical Satellite IRAS, the Japanese Akari satellite, and the NEOWISE mission of NASA's WISE telescope (WISE), Lyka measures (28.10±3.9), (31.29±0.49) and (34.878±0.184) kilometers in diameter and its surface has an albedo of (0.0891±0.031), (0.072±0.003) and (0.056±0.008), respectively.[6][7][8] The Collaborative Asteroid Lightcurve Link derives an albedo of 0.0520 and a diameter of 27.89 km based on an absolute magnitude of 11.6.[12] Further published mean-diameters by the WISE team include (21.60±4.99 km), (26.65±9.28 km), (34.789±2.565 km) and (37.843±0.227 km) with albedos between (0.026±0.009) and (0.05±0.02).[5][12] An asteroid occultation, observed on 4 March 2005, gave a best-fit ellipse dimension of 28.0 × 28.0 kilometers.[5] These timed observations are taken when the asteroid passes in front of a distant star. However the quality of the measurement is rated poorly.[5]

    References
    1. "917 Lyka (A915 RR)". Minor Planet Center. Retrieved 23 February 2020.
    2. Schmadel, Lutz D. (2007). "(917) Lyka". Dictionary of Minor Planet Names. Springer Berlin Heidelberg. p. 82. doi:10.1007/978-3-540-29925-7_918. ISBN 978-3-540-00238-3.
    3. "JPL Small-Body Database Browser: 917 Lyka (A915 RR)" (2020-02-05 last obs.). Jet Propulsion Laboratory. Retrieved 23 February 2020.
    4. "Asteroid 917 Lyka – Proper Elements". AstDyS-2, Asteroids – Dynamic Site. Retrieved 23 February 2020.
    5. "Asteroid 917 Lyka". Small Bodies Data Ferret. Retrieved 23 February 2020.
    6. 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 23 February 2020.
    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 23 February 2020. (online, AcuA catalog p. 153)
    8. 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.
    9. Lazzaro, D.; Angeli, C. A.; Carvano, J. M.; Mothé-Diniz, T.; Duffard, R.; Florczak, M. (November 2004). "S3OS2: the visible spectroscopic survey of 820 asteroids" (PDF). Icarus. 172 (1): 179–220. Bibcode:2004Icar..172..179L. doi:10.1016/j.icarus.2004.06.006. Retrieved 23 February 2020.
    10. Behrend, Raoul. "Asteroids and comets rotation curves – (917) Lyka". Geneva Observatory. Retrieved 23 February 2020.
    11. Carreño, Alfonso; Arce, Enrique; Fornas, Gonzalo; Mas, Vicente (April 2019). "Eleven Main-belt Asteroids and One Near-Earth Asteroid Lightcurves at Asteroids Observers (OBAS) - MPPD: 2017 May - 2019 Jan" (PDF). Minor Planet Bulletin. 46 (2): 200–203. Bibcode:2019MPBu...46..200C. ISSN 1052-8091.
    12. "LCDB Data for (917) Lyka". Asteroid Lightcurve Database (LCDB). Retrieved 23 February 2020.
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