789 Lena

789 Lena, provisional designation 1914 UU, is a metallic asteroid from the middle region of the asteroid belt, approximately 24 kilometers in diameter. It was discovered on 24 June 1914, by Soviet–Russian astronomer Grigory Neujmin at Simeiz Observatory on the Crimean peninsula, and named after the discoverer's mother.[13]

789 Lena
Discovery [1]
Discovered byG. Neujmin
Discovery siteSimeiz Obs.
Discovery date24 June 1914
Designations
(789) Lena
Pronunciation/ˈleɪnə/[2]
Named after
Elena Neujmina
(discoverer's family)[3]
1914 UU · 1970 CE
main-belt · (middle) [4]
Orbital characteristics [1]
Epoch 16 February 2017 (JD 2457800.5)
Uncertainty parameter 0
Observation arc81.69 yr (29,837 days)
Aphelion3.0817 AU
Perihelion2.2907 AU
2.6862 AU
Eccentricity0.1472
4.40 yr (1,608 days)
110.02°
0° 13m 26.04s / day
Inclination10.781°
232.62°
44.006°
Physical characteristics
Dimensions20.56±0.34 km[5]
22.483±0.306[6]
23.871±0.162 km[7]
24.18 km (calculated)[4]
5.84239±0.00001 h[8]
5.848±0.001 h[9]
5.85±0.05 h[10]
22 h[11]
0.10 (assumed)[4]
0.1373±0.0147[7]
0.153±0.028[6]
0.186±0.007[5]
SMASS = X [1] · M [7] · X [4]
10.47±0.60[12] · 10.9[5][7] · 11.2[1][4]

    Orbit and classification

    Lena orbits the Sun in the middle main-belt at a distance of 2.3–3.1 AU once every 4 years and 5 months (1,608 days). Its orbit has an eccentricity of 0.15 and an inclination of 11° with respect to the ecliptic.[1] Lena's observation arc begins with its first used observation made at Yerkes Observatory in 1935, or 21 years after its official discovery observation at Simeiz.[13]

    Although its orbital elements resemble those of the asteroids in the Eunomia family, true members of this family have a S-type composition, so it is almost certainly an unrelated interloper.

    Physical characteristics

    In the SMASS taxonomy, Lena is an X-type asteroid. It has also been characterized as a metallic M-type asteroid by NASA's Wide-field Infrared Survey Explorer (WISE).[7]

    Rotation period

    In 1993, a rotational lightcurve which was later proven incorrect, was obtained from photometric observations at the Félix Aguilar Observatory, Argentina. It gave an unusual lightcurve, indicating a very irregular shape and/or a relatively long rotation period of 22 hours with an exceptionally high amplitude of 1.5 in magnitude (U=0).[11]

    In August and September 2007, two reliable lightcurves were obtained by Italian astronomer Silvano Casulli and by members at the U.S.Oakley Observatory. Lightcurve analysis gave a period of 5.848±0.001 and 5.85±0.05 hours, with a brightness variation of 0.50 and of 0.40 magnitude, respectively (U=3/2+).[lower-alpha 1][9][10]

    Diameter and albedo

    According to the space-based surveys carried out by the Japanese Akari satellite and the NEOWISE mission of the WISE telescope, Lena measures between 20.6 and 23.9 kilometers in diameter, and its surface has an albedo of 0.137–0.186.[5][6][7] The Collaborative Asteroid Lightcurve Link assumes a much lower albedo of 0.10 and calculates a diameter of 24.2 kilometer, as the lower the albedo (reflectivity), the larger a body's diameter, at a constant absolute magnitude (brightness).[4]

    Naming

    This minor planet was named in honor of Elena ("Lena") Petrovna Neujmina (1860–1942), mother of the discovering astronomer Grigory Neujmin.[3]

    Notes
    1. The Collaborative Asteroid Lightcurve Link (CALL) assigns a quality code to light-curve observations, ranging from 0 ("result later proven incorrect") to 3 ("secure result within the precision given and no ambiguity"). The 1993-lightcurve obtained at the Félix Aguilar Observatory was rated "0", while CALL tags the more recent 2007-observations with a quality code of "2+" and "3", respectively. Summary figures at Collaborative Asteroid Lightcurve Link (CALL) for (789) Lena

    References
    1. "JPL Small-Body Database Browser: 789 Lena (1914 UU)" (2016-11-08 last obs.). Jet Propulsion Laboratory. Retrieved 12 December 2016.
    2. Noah Webster (1884) A Practical Dictionary of the English Language
    3. Schmadel, Lutz D. (2007). "(789) Lena". Dictionary of Minor Planet Names – (789) Lena. Springer Berlin Heidelberg. p. 74. doi:10.1007/978-3-540-29925-7_790. ISBN 978-3-540-00238-3.
    4. "LCDB Data for (789) Lena". Asteroid Lightcurve Database (LCDB). Retrieved 4 July 2016.
    5. 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. (online, AcuA catalog p. 153)
    6. 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 12 December 2016.
    7. 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.
    8. Durech, J.; Hanus, J.; Oszkiewicz, D.; Vanco, R. (March 2016). "Asteroid models from the Lowell photometric database". Astronomy and Astrophysics. 587: 6. arXiv:1601.02909. Bibcode:2016A&A...587A..48D. doi:10.1051/0004-6361/201527573. Retrieved 4 July 2016.
    9. Behrend, Raoul. "Asteroids and comets rotation curves – (789) Lena". Geneva Observatory. Retrieved 4 July 2016.
    10. Shipley, Heath; Dillard, Alex; Kendall, Jordan; Reichert, Matthew; Sauppe, Jason; Shaffer, Nelson; et al. (September 2008). "Asteroid Lightcurve Analysis at the Oakley Observatory - September 2007". The Minor Planet Bulletin. 35 (3): 99–102. Bibcode:2008MPBu...35...99S. ISSN 1052-8091. Retrieved 4 July 2016.
    11. Gil-Hutton, R. (October 1995). "Research Note: Photometry of Asteroids 359 Georgia and 789 Lena". Revista Mexicana de Astronomía y Astrofísica. 31: 143. Bibcode:1995RMxAA..31..143G. Retrieved 4 July 2016.
    12. 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 4 July 2016.
    13. "789 Lena (1914 UU)". Minor Planet Center. Retrieved 4 July 2016.

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