817 Annika

817 Annika (prov. designation: A916 CD or 1916 YW) is a background asteroid in the region of the Eunomia family, located in the central portion of the asteroid belt. It was discovered on 6 February 1916, by German astronomer Max Wolf at the Heidelberg-Königstuhl State Observatory in southwest Germany.[1] The stony S-type asteroid (Sl) has a rotation period of 10.56 hours and measures approximately 23 kilometers (14 miles) in diameter. Any reference of the asteroid's name to a person is unknown.[3]

817 Annika
Discovery [1]
Discovered byM. F. Wolf
Discovery siteHeidelberg Obs.
Discovery date6 February 1916
Designations
(817) Annika
Pronunciation/ˈænɪkə/ German: [ˈanikaː][2]
Named after
unknown [3]
A916 · CD 1916 YW
Orbital characteristics [4]
Epoch 31 May 2020 (JD 2459000.5)
Uncertainty parameter 0
Observation arc103.99 yr (37,982 d)
Aphelion3.0570 AU
Perihelion2.1231 AU
2.5900 AU
Eccentricity0.1803
4.17 yr (1,523 d)
61.065°
0° 14m 11.4s / day
Inclination11.336°
125.47°
285.18°
Physical characteristics
Dimensions22.0 km × 22.0 km
Mean diameter
Mean density
~2.7 g/cm3 (estimate)[13]

    Orbit and classification

    Annika is a non-family asteroid of the main belt's background population when applying the hierarchical clustering method (HCM) to its proper orbital elements by Nesvorný as well as by Milani and Knežević (AstDyS).[5][6] In the 1995 HCM-analysis by Zappalà,[8] however, Annika is a member of the Eunomia family (502), a prominent family of stony asteroids and the largest one in the intermediate main belt with more than 5,000 members.[7] It orbits the Sun in the central main-belt at a distance of 2.1–3.1 AU once every 4 years and 2 months (1,523 days; semi-major axis of 2.59 AU). Its orbit has an eccentricity of 0.18 and an inclination of 11° with respect to the ecliptic.[4] The body's observation arc begins with its official discovery observation at Heidelberg Observatory on 6 February 1916.[1]

    Naming

    "Annika" is a common German feminine given name. Any reference to a person or occurrence for the naming of this minor planet is unknown.[3]

    Unknown meaning

    Among the many thousands of named minor planets, Annika is one of 120 asteroids, for which no official naming citation has been published. All of these asteroids have low numbers, the first being 164 Eva. The last asteroid with a name of unknown meaning is 1514 Ricouxa. They were discovered between 1876 and the 1930s, predominantly by astronomers Auguste Charlois, Johann Palisa, Max Wolf and Karl Reinmuth.[17]

    Physical characteristics

    In the Tholen-like taxonomy of the Small Solar System Objects Spectroscopic Survey (S3OS2), Annika is a common, stony S-type asteroid, while in the SMASS-like taxonomic variant of the S3OS2 survey, it is an Sl-subtype which transitions from the S-type to the uncommon L-type asteroid.[6][16]

    Rotation period

    In October 2002, a rotational lightcurve of Annika was obtained from photometric observations by Colin Bembrick at Mount Tarana Observatory (431), Australia, in collaboration with Greg Bolt and Tom Richards near Perth and Melbourne, respectively. Lightcurve analysis gave a well-defined rotation period of 10.560±0.004 hours with a brightness variation of 0.27±0.02 magnitude (U=3).[14] This period was confirmed by Gérald Rousseau in March 2012, who determined a very similar period of 10.564±0.001 hours with an amplitude of 0.16±0.02 magnitude (U=3).[15]

    Diameter and albedo

    According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer (WISE), and the Japanese Akari satellite, Annika measures (22.05±1.7), (22.891±0.100) and (23.02±0.34) kilometers in diameter and its surface has an albedo of (0.1740±0.030), (0.191±0.027) and (0.163±0.006), respectively.[9][10][11][12] The Collaborative Asteroid Lightcurve Link derives an albedo of 0.2062 and a diameter of 22.20 kilometers based on an absolute magnitude of 10.6.[7] Alternative mean-diameter measurements published by the WISE team include (17.65±4.40 km), (22.59±5.70 km), (24.38±0.50 km) and (26.569±0.191 km) with corresponding albedos of (0.26±0.13), (0.22±0.17), (0.187±0.025) and (0.1199±0.0098).[6][7]

    On 26 August 2010, an asteroid occultation of Annika gave a best-fit ellipse dimension of (22.0 km × 22.0 km). These timed observations are taken when the asteroid passes in front of a distant star. However, these two observations have received a poor quality rating.[6]

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    References
    1. "817 Annika (A916 CD)". Minor Planet Center. Retrieved 25 March 2020.
    2. (German Names)
    3. Schmadel, Lutz D. (2007). "(817) Annika". Dictionary of Minor Planet Names. Springer Berlin Heidelberg. p. 76. doi:10.1007/978-3-540-29925-7_818. ISBN 978-3-540-00238-3.
    4. "JPL Small-Body Database Browser: 817 Annika (A916 CD)" (2020-02-02 last obs.). Jet Propulsion Laboratory. Retrieved 25 March 2020.
    5. "Asteroid 817 Annika – Proper Elements". AstDyS-2, Asteroids – Dynamic Site. Retrieved 25 March 2020.
    6. "Asteroid 817 Annika – Nesvorny HCM Asteroid Families V3.0". Small Bodies Data Ferret. Retrieved 25 March 2020.
    7. "LCDB Data for (817) Annika". Asteroid Lightcurve Database (LCDB). Retrieved 25 March 2020.
    8. 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 25 March 2020.} (PDS main page)
    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 25 March 2020.
    10. 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 25 March 2020.
    11. 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.
    12. 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 25 March 2020. (online, AcuA catalog p. 153)
    13. Krasinsky, G. A.; Pitjeva, E. V.; Vasilyev, M. V.; Yagudina, E. I. (July 2002). "Hidden Mass in the Asteroid Belt". Icarus. 158 (1): 98–105. Bibcode:2002Icar..158...98K. doi:10.1006/icar.2002.6837. ISSN 0019-1035.
    14. Bembrick, Colin; Bolt, Greg; Richards, Tom (2003). "Lightcurves and period determination for 817 Annika" (PDF). Minor Planet Bulletin. 30 (2): 20–21. Bibcode:2003MPBu...30...20B. ISSN 1052-8091.
    15. Behrend, Raoul. "Asteroids and comets rotation curves – (817) Annika". Geneva Observatory. Retrieved 25 March 2020.
    16. 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 25 March 2020.
    17. Schmadel, Lutz D. (2007). "Appendix 11 – Minor Planet Names with Unknown Meaning". Dictionary of Minor Planet Names – Fifth Revised and Enlarged revision. Springer Berlin Heidelberg. pp. 927–929. ISBN 978-3-540-00238-3.
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