2867 Šteins (provisional designation 1969 VC) is an irregular, diamond-shaped background asteroid from the inner regions of the asteroid belt, approximately 5 kilometers (3.1 miles) in diameter. It was discovered on 4 November 1969 by Soviet astronomer Nikolai Chernykh at the Crimean Astrophysical Observatory in Nauchnij on the Crimean peninsula.[1] In September 2008, ESA's spacecraft Rosetta flew by Šteins, making it one of few minor planets ever visited by a spacecraft. The bright E-type asteroid features 23 named craters and has a rotation period of 6.05 hours.[8] It was named for Soviet Latvian astronomer Kārlis Šteins.[1]
Šteins is a non-family asteroid from the main belt's background population.[3][4] It orbits the Sun in the inner asteroid belt at a distance of 2.0–2.7AU once every 3 years and 8 months (1,327 days; semi-major axis of 2.36AU). Its orbit has an eccentricity of 0.15 and an inclination of 10° with respect to the ecliptic.[2] The body's observation arc begins with a precovery, taken at the Palomar Observatory in November 1951, or 18 years prior to its official discovery observation.[1]
Rosetta flyby
Animation of Rosetta's trajectory from 2 March 2004 to 9 September 2016 Rosetta·67P·Earth·Mars·21 Lutetia·2867 Šteins
On 5 September 2008, the Rosetta space probe flew by Šteins at a distance of 800km and a relatively slow speed of 8.6km/s. Despite the short duration of this encounter (approximately 7 minutes in total), a great amount of data was obtained by the 15 scientific instruments operating on board the Rosetta spacecraft.[14] This was the first of two planned asteroid flybys performed by the probe, the second being to the much larger 21 Lutetia in 2010.[15] The timing of the fly-by meant that the asteroid was illuminated by the sun from the perspective of the spacecraft, making the transmitted images clear. The European Space Operations Centre streamed a press conference on Šteins later that day.[16]
Naming
This minor planet was named in memory of Kārlis Šteins (1911–1983), a Latvian and Soviet astronomer. He was a long-time observatory director at the University of Latvia in Riga and designed astronomical instruments. Šteins is known for his work on cometary cosmogony and the study of Earth's rotation.[1] The official naming citation was published by the Minor Planet Center on 18 September 1986 (M.P.C. 11157).[17]
Features on Šteins
Further information: List of craters on Šteins
On 11 May 2012, IAU's Working Group for Planetary System Nomenclature announced a naming system for geographical features on Šteins.[18] Inspired by the asteroid's gem-like shape, its crater are given the English-language names of precious stones, with the largest being named Diamond crater (see below).
Except for the montes of Mercury and the lunar maria (and proposed for 2 Pallas and 7 Iris), the craters of Šteins are the only features in the Solar System whose names are not derived from proper nouns.[19] In addition, a distinct region on the asteroid has been named Chernykh Regio after the discoverer, Nikolai Chernykh.[20]
Physical characteristics
A study published in 2006 by astronomers at the European Southern Observatory showed that Šteins is an E-type asteroid with a diameter of approximately 4.6 kilometers.[9] After the Rosetta flyby, the ESA described Šteins as a "diamond in the sky", as it has a wide body that tapers into a point. The wide section is dominated by the large Diamond crater with a diameter of 2.1 kilometers, which surprised scientists, who were at first amazed the asteroid survived such an impact,[21] while later it turned out that the crater-to-body diameter ratio of 0.79 is in fact not abnormally large as it follows an already established trend.[22] Besides its irregular in shape, it does not have any moons.[23]
Diameter and albedo
According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer and observations by the Spitzer Space Telescope, Šteins measures 5.16 and 4.92 kilometers in diameter and its surface has an albedo of 0.30 and 0.34, respectively.[6][7] Its overall Bond albedo is 0.24 ± 0.01.[24] In 2012, the photographs of Šteins taken by Rosetta using stereophotoclinometry allowed scientists to determine that the asteroid's dimensions are 6.83 × 5.70 × 4.42 kilometers, which equates to a mean diameter in volume of 5.26km.[5] (Asteroid 129167 Dianelambert was later named for the scientist using this 3D-method.) The Collaborative Asteroid Lightcurve Link adopts an albedo of 0.34 and a diameter of 4.9 kilometers with an absolute magnitude of 13.36.[8]
Lightcurves and poles
Studying the asteroid with Rosetta space probe onboard OSIRIS cameras shortly before its flyby showed via a lightcurve analysis that Šteins has a rotation period of 6.052±0.007 hours.[25][23] The results of the rotational lightcurve agree with ground-based photometric observations of Šteins with a period of 6.049 hours and a brightness amplitude between 0.18 and 0.31 magnitude (U=3/3).[8][10][12][13][26][27][lower-alpha 1]
A lightcurve inversion also modeled a concurring sidereal period of 6.04681 hours and determined a spin axis at (250.0°, −89.0°) in ecliptic coordinates (λ,β). The modeling was done by compiling a set of 26 previously obtained visible lightcurves.[28]
Lightcurve plot of 2867 Steins, Palmer Divide Observatory by B. D. Warner (2004). Rotation period of 6.05±0.01 hours with a brightness amplitude of 0.30 mag. Quality code is 3-. Summary figures for (2867) Šteins at the LCDB.
Mainzer, A. K.; Bauer, J. M.; Cutri, R. M.; Grav, T.; Kramer, E. A.; Masiero, J. R.; etal. (June 2016). "NEOWISE Diameters and Albedos V1.0". NASA Planetary Data System: EAR-A-COMPIL-5-NEOWISEDIAM-V1.0. Bibcode:2016PDSS..247.....M. Retrieved 31 August 2018.
Fornasier, S.; Belskaya, I.; Fulchignoni, M.; Barucci, M. A.; Barbieri, C. (April 2006). "First albedo determination of 2867 Steins, target of the Rosetta mission". Astronomy and Astrophysics. 449 (2): L9–L12. arXiv:astro-ph/0602631. Bibcode:2006A&A...449L...9F. doi:10.1051/0004-6361:20064913.
Belskaya, I. N.; Fornasier, S.; Tozzi, G. P.; Gil-Hutton, R.; Cellino, A.; Antonyuk, K.; etal. (March 2017). "Refining the asteroid taxonomy by polarimetric observations". Icarus. 284: 30–42. Bibcode:2017Icar..284...30B. doi:10.1016/j.icarus.2016.11.003.
Weissman, Paul R.; Lowry, Stephen C.; Choi, Young-Jun (August 2005). "CCD Photometry of Asteroid 2867 Steins: Flyby Target of the Rosetta Mission". American Astronomical Society. 37: 644. Bibcode:2005DPS....37.1528W.
M. A. Barucci; M. Fulchignoni & A. Rossi (2007). "Rosetta Asteroid Targets: 2867 Steins and 21 Lutetia". Space Science Reviews. 128 (1–4): 67–78. Bibcode:2007SSRv..128...67B. doi:10.1007/s11214-006-9029-6.
"Target: Steins". IAU–Working Group for Planetary System Nomenclature (WGPSN). Archived from the original on 3 October 2018. Retrieved 14 September 2015.
Spjuth, S.; Jorda, L.; Lamy, P. L.; Keller, H. U.; Li, J.-Y. (November 2012). "Disk-resolved photometry of Asteroid (2867) Steins". Icar. 221 (2): 1101–1118. Bibcode:2012Icar..221.1101S. doi:10.1016/j.icarus.2012.06.021. ISSN0019-1035.
Küppers, M.; Mottola, S.; Lowry, S. C.; A'Hearn, M. F.; Barbieri, C.; Barucci, M. A.; etal. (January 2007). "Determination of the light curve of the Rosetta target asteroid (2867) Steins by the OSIRIS cameras onboard Rosetta". Astronomy and Astrophysics. 462 (1): L13–L16. arXiv:astro-ph/0612097. Bibcode:2007A&A...462L..13K. doi:10.1051/0004-6361:20066694.
Warner, Brian D. (September 2004). "Lightcurve analysis for numbered asteroids 301, 380, 2867, 8373, 25143, and 31368". The Minor Planet Bulletin. 31 (3): 67–70. Bibcode:2004MPBu...31...67W. ISSN1052-8091.
Weissman, P. R.; Lowry, S. C.; Choi, Y.-J. (May 2007). "Photometric observations of Rosetta target asteroid 2867 Steins". Astronomy and Astrophysics. 466 (2): 737–742. arXiv:astro-ph/0702339. Bibcode:2007A&A...466..737W. doi:10.1051/0004-6361:20066409.
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