1621 Druzhba

1621 Druzhba, provisional designation 1926 TM, is a stony Florian asteroid and relatively slow rotator from the inner regions of the asteroid belt, approximately 10 kilometers in diameter. It was discovered on 1 October 1926, by Russian astronomer Sergey Belyavsky at Simeiz Observatory on the Crimean peninsula.[13] It was named after the Russian word for friendship.[2]

1621 Druzhba
Shape model of Druzhba from its lightcurve
Discovery [1]
Discovered byS. Belyavskyj
Discovery siteSimeiz Obs.
Discovery date1 October 1926
Designations
(1621) Druzhba
Named after
дружба – lit. friendship
(in Russian)[2]
1926 TM · 1927 AE
1931 EO · 1946 UH
1949 QS1 · 1951 EK1
1951 ER1 · 1958 GA
1979 QP4
main-belt · Flora [3]
Orbital characteristics [1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc90.49 yr (33,052 days)
Aphelion2.4948 AU
Perihelion1.9650 AU
2.2299 AU
Eccentricity0.1188
3.33 yr (1,216 days)
73.187°
0° 17m 45.6s / day
Inclination3.1730°
181.88°
238.14°
Physical characteristics
Dimensions9.05 km (derived)[3]
9.08±0.8 km[4]
11.70±0.20 km[5]
12.694±0.296 km[6]
12 h (dated)[7]
47.9±0.5 h (dated)[8]
99.100±0.005 h[9]
99.20±0.03 h[10]
0.2373±0.046[4]
0.243 (derived)[3]
0.244±0.039[6]
0.312±0.012[5]
Tholen = S [1] · S [3][11]
B–V = 0.898[1]
U–B = 0.503[1]
11.63[1][5][6] · 12.37±0.09[3][7][12] · 12.39[4] · 12.53±0.29[11]

    Classification and orbit

    Druzhba is a member of the Flora family, one of the largest collisional groups of stony asteroids in the main-belt. It orbits the Sun at a distance of 2.0–2.5 AU once every 3 years and 4 months (1,216 days). Its orbit has an eccentricity of 0.12 and an inclination of 3° with respect to the ecliptic.[1] Druzhba's observation arc begins at the discovering observatory, one week after its official discovery observation.[13]

    Physical characteristics

    In the Tholen classification, Druzhba is a common S-type asteroid.[1]

    Rotation period

    In August 2009, American amateur astronomer Robert D. Stephens obtained a rotational lightcurve of Druzhba from photometric observations. In gave a well-defined rotation period of 99.20 hours with a change in brightness of 0.75 magnitude (U=3)[10] A 2016-published modeled light-curve of 99.100 hours concurred with the result.[9]

    This makes it a relatively slow rotator, as the vast majority of minor planets rotate every 2 to 20 hours around their axis. Druzhba's long rotation period was particularly difficulty to measure: Previously, observations by Richard Ditteon at Oakley Observatory gave a period solution of 47.9 hours (Δmag 1.0; U=1),[8] while Polish astronomer Wiesław Wiśniewski obtained a period of only 12 hours in the late 1980s (Δmag 0.16; U=1).[7]

    Diameter and albedo

    According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the Japanese Akari satellite, and NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Druzhba measures between 9.08 and 12.69 kilometers in diameter, and its surface has an albedo between 0.237 and 0.312.[4][6][5]

    Based on an absolute magnitude of 12.37, the Collaborative Asteroid Lightcurve Link derives a diameter of 9.05 kilometers and an albedo of 0.243 – similar to the albedo of 8 Flora, the family's largest member and namesake.[3]

    Naming

    This minor planet was named Druzhba, this is a Slavic word for friendship and the name of several cities, towns and other localities in Russia, Ukraine, Bulgaria and Kazakhstan. The asteroid's name was proposed by the Institute of Theoretical Astronomy in St. Petersburg.[2] The official naming citation was published by the Minor Planet Center on 1 June 1967 (M.P.C. 2740).[14]

    References
    1. "JPL Small-Body Database Browser: 1621 Druzhba (1926 TM)" (2017-03-29 last obs.). Jet Propulsion Laboratory. Retrieved 4 June 2017.
    2. Schmadel, Lutz D. (2007). "(1621) Druzhba". Dictionary of Minor Planet Names – (1621) Druzhba. Springer Berlin Heidelberg. p. 128. doi:10.1007/978-3-540-29925-7_1622. ISBN 978-3-540-00238-3.
    3. "LCDB Data for (1621) Druzhba". Asteroid Lightcurve Database (LCDB). Retrieved 28 December 2016.
    4. 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.
    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. Retrieved 17 October 2019. (online, AcuA catalog p. 153)
    6. Masiero, Joseph R.; Mainzer, A. K.; Grav, T.; Bauer, J. M.; Cutri, R. M.; Nugent, C.; et al. (November 2012). "Preliminary Analysis of WISE/NEOWISE 3-Band Cryogenic and Post-cryogenic Observations of Main Belt Asteroids". The Astrophysical Journal Letters. 759 (1): 5. arXiv:1209.5794. Bibcode:2012ApJ...759L...8M. doi:10.1088/2041-8205/759/1/L8. Retrieved 28 December 2016.
    7. Wisniewski, W. Z.; Michalowski, T. M.; Harris, A. W.; McMillan, R. S. (March 1995). "Photoelectric Observations of 125 Asteroids". Abstracts of the Lunar and Planetary Science Conference. 26: 1511. Bibcode:1995LPI....26.1511W. Retrieved 28 December 2016.
    8. Ditteon, Richard; Hawkins, Scot (September 2007). "Asteroid Lightcurve Analysis at the Oakley Observatory - October-November 2006". The Minor Planet Bulletin. 34 (3): 59–64. Bibcode:2007MPBu...34...59D. ISSN 1052-8091. Retrieved 28 December 2016.
    9. Hanus, J.; Durech, J.; Oszkiewicz, D. A.; Behrend, R.; Carry, B.; Delbo, M.; et al. (February 2016). "New and updated convex shape models of asteroids based on optical data from a large collaboration network". Astronomy and Astrophysics. 586: 24. arXiv:1510.07422. Bibcode:2016A&A...586A.108H. doi:10.1051/0004-6361/201527441.
    10. Stephens, Robert D. (January 2010). "Asteroids Observed from GMARS and Santana Observatories: 2009 June - September". The Minor Planet Bulletin. 37 (1): 28–29. Bibcode:2010MPBu...37...28S. ISSN 1052-8091. Retrieved 28 December 2016.
    11. 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 28 December 2016.
    12. Pravec, Petr; Harris, Alan W.; Kusnirák, Peter; Galád, Adrián; Hornoch, Kamil (September 2012). "Absolute magnitudes of asteroids and a revision of asteroid albedo estimates from WISE thermal observations". Icarus. 221 (1): 365–387. Bibcode:2012Icar..221..365P. doi:10.1016/j.icarus.2012.07.026. Retrieved 28 December 2016.
    13. "1621 Druzhba (1926 TM)". Minor Planet Center. Retrieved 28 December 2016.
    14. 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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