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21088 Chelyabinsk
Discovery
Discovered by	E. W. Elst
Discovery site	La Silla Obs.
Discovery date	30 January 1992
Designations
MPC designation	(21088) Chelyabinsk
Named after	Chelyabinsk (city and meteor)
Alternative designations	1992 BL2
Minor planet category	NEO · Amor ; Mars-crosser
Orbital characteristics
	Epoch 4 September 2017 (JD 2458000.5)
	Uncertainty parameter 0
Observation arc	27.41 yr (10,012 days)
Aphelion	2.1135 AU
Perihelion	1.2996 AU
Semi-major axis	1.7065 AU
Eccentricity	0.2384
Orbital period (sidereal)	2.23 yr (814 days)
Mean anomaly	318.92°
Mean motion	0° 26m 31.56s / day
Inclination	38.455°
Longitude of ascending node	297.85°
Argument of perihelion	27.133°
Earth MOID	0.3083 AU · 120.1 LD
Physical characteristics
Dimensions	2.79±0.10 km; 3.46±0.25 km; 4.23 km (taken); 4.231±0.113 km; 4.232 km
Synodic rotation period	22.426±0.02 h; 22.49 h
Geometric albedo	0.1794; 0.206; 0.257±0.038; 0.26±0.32; 0.37±0.06
Spectral type	Q · L · S ; B–V = 0.855±0.073; V–R = 0.464±0.015 ; V–I = 0.910±0.032
Absolute magnitude (H)	13.86±0.14 (R) · 14.00 · 14.2 · 14.29±0.24 · 14.3 · 14.35±0.149 · 14.40

21088 Chelyabinsk (provisional designation 1992 BL₂) is a stony asteroid and near-Earth object of the Amor group, approximately 4 kilometers in diameter. It was discovered on 30 January 1992, by Belgian astronomer Eric Elst at ESO's La Silla Observatory in northern Chile. The asteroid was named after the Russian city of Chelyabinsk and for its spectacular Chelyabinsk meteor event in 2013.^[2] It is not related to the Chelyabinsk impactor.

Classification and orbit

Chelyabinsk orbits the Sun at a distance of 1.3–2.1 AU once every 2 years and 3 months (814 days). Its orbit has an eccentricity of 0.24 and an inclination of 38° with respect to the ecliptic. A first precovery was taken during the Digitized Sky Survey at the Australia Siding Spring Observatory in January 1990, extending the asteroid's observation arc by 2 years prior to its official discovery at La Silla.^[2]

Close approaches

As a near-Earth object, Chelyabinsk has a low Earth minimum orbit intersection distance of 0.3083 AU (46,100,000 km), which translates into 120.1 lunar distances (LD). This is, however, far too large to make it a potentially hazardous asteroid, which have intersection distances of less than 20 LD.^[1] It also crosses the orbit of Mars at 1.666 AU which makes it a Mars-crossing asteroid. In August 2142, it will approach Mars at 0.0986 AU (14,800,000 km).^[1]

Physical characteristics

Chelyabinsk has been characterized as both a Q-type and L-type asteroid.^[10]^[11] It is also a generically assumed S-type asteroid.^[5]

Lightcurves

Two rotational light-curves of Chelyabinsk were obtained by Czech astronomer Petr Pravec at Ondřejov Observatory in December 2002 and September 2004, respectively. They gave a rotation period of 22.490 and 22.426 hours, each with a brightness variation of 0.13 magnitude (U=n.a./3-).^[a]^[b]

Diameter and albedo

According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer (WISE), Chelyabinsk measures between 2.79 and 4.2 kilometers in diameter and its surface has an albedo between 0.21 and 0.37,^[6]^[7]^[8] while observations by the Japanese Akari satellite gave an albedo of 0.26 and a diameter of 3.5 kilometers.^[4] The Collaborative Asteroid Lightcurve Link adopts Petr Pravec's revised WISE results, that is, a diameter of 4.23 kilometers and an albedo of 0.179 based on an absolute magnitude of 14.35.^[5]^[8]

Naming

This minor planet is named after the Russian city Chelyabinsk, located in the Ural region. The city is well known for the Chelyabinsk meteor, a 20-meter sized, extremely bright fireball that exploded to the south of the city at an altitude of 30 kilometers on 15 February 2013. The indirect effects of the explosion injured more than 1,500 people.^[2] The official naming citation was published by the Minor Planet Center (MPC) on 21 August 2013 (M.P.C. 84674).^[14]

Erratum

Originally, the name "Chelyabinsk" was erroneously given by the MPC to the numerically similar asteroid (20188) 1997 AC₁₈ on 22 July (M.P.C. 84379). The wrong designation 20188 Chelyabinsk was deleted in the subsequent publication of the Minor Planet Circulars on 21 August 2013 (M.P.C. 84385) ^[14]

Notes

^ ^a ^b ^c ^d Pravec (2002 and 2004) web: rotation period of 22.49 and 22.426±0.02 hours, both with a brightness amplitude of 0.13 mag. Summary figures of (21088) Chelyabinsk at the LCDB and Pravec, P.; Wolf, M.; Sarounova, L. (2002/2004)
^ ^a ^b Lightcurve plot by Pravec from 7 June 2005 with period of 22.431 hours. Data sheet from unpublished observations at Ondrejov Asteroid Photometry Project

References

^ ^a ^b ^c ^d ^e ^f "JPL Small-Body Database Browser: 21088 Chelyabinsk (1992 BL2)" (2016-02-19 last obs.). Jet Propulsion Laboratory. Retrieved 12 October 2016.
^ ^a ^b ^c ^d ^e "21088 Chelyabinsk (1992 BL2)". Minor Planet Center. Retrieved 12 October 2016.
^ ^a ^b Nugent, C. R.; Mainzer, A.; Bauer, J.; Cutri, R. M.; Kramer, E. A.; Grav, T.; et al. (September 2016). "NEOWISE Reactivation Mission Year Two: Asteroid Diameters and Albedos". The Astronomical Journal. 152 (3): 12. arXiv:1606.08923. Bibcode:2016AJ....152...63N. doi:10.3847/0004-6256/152/3/63.
^ ^a ^b ^c ^d 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)
^ ^a ^b ^c ^d ^e "LCDB Data for (21088) Chelyabinsk". Asteroid Lightcurve Database (LCDB). Retrieved 12 October 2016.
^ ^a ^b ^c ^d 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. S2CID 35447010.
^ ^a ^b Mainzer, A.; Grav, T.; Bauer, J.; Masiero, J.; McMillan, R. S.; Cutri, R. M.; et al. (December 2011). "NEOWISE Observations of Near-Earth Objects: Preliminary Results". The Astrophysical Journal. 743 (2): 17. arXiv:1109.6400. Bibcode:2011ApJ...743..156M. doi:10.1088/0004-637X/743/2/156. S2CID 239991.
^ ^a ^b ^c ^d ^e 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.
^ Thomas, C. A.; Trilling, D. E.; Emery, J. P.; Mueller, M.; Hora, J. L.; Benner, L. A. M.; et al. (September 2011). "ExploreNEOs. V. Average Albedo by Taxonomic Complex in the Near-Earth Asteroid Population". The Astronomical Journal. 142 (3): 12. Bibcode:2011AJ....142...85T. doi:10.1088/0004-6256/142/3/85.
^ ^a ^b Thomas, Cristina A.; Emery, Joshua P.; Trilling, David E.; Delbó, Marco; Hora, Joseph L.; Mueller, Michael (January 2014). "Physical characterization of Warm Spitzer-observed near-Earth objects". Icarus. 228: 217–246. arXiv:1310.2000. Bibcode:2014Icar..228..217T. doi:10.1016/j.icarus.2013.10.004. S2CID 119278697.
^ ^a ^b ^c Carry, B.; Solano, E.; Eggl, S.; DeMeo, F. E. (April 2016). "Spectral properties of near-Earth and Mars-crossing asteroids using Sloan photometry". Icarus. 268: 340–354. arXiv:1601.02087. Bibcode:2016Icar..268..340C. doi:10.1016/j.icarus.2015.12.047. S2CID 119258489.
^ ^a ^b ^c Ye, Q.-z. (February 2011). "BVRI Photometry of 53 Unusual Asteroids". The Astronomical Journal. 141 (2): 8. arXiv:1011.0133. Bibcode:2011AJ....141...32Y. doi:10.1088/0004-6256/141/2/32. S2CID 119307210.
^ 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. S2CID 53493339.
^ ^a ^b "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 12 October 2016.