Except for the montesofMercury 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.[16] In addition, a distinct region on the asteroid has been named Chernykh Regio after the discoverer, Nikolai Chernykh.[17]
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,[18] 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.[19] Besides its irregular in shape, it does not have any moons.[20]
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.[21] 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 5.26 km.[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]
Studying the asteroid with Rosetta space probe onboard OSIRIS cameras shortly before its flyby showed via a lightcurve analysis that Šteins has a rotation periodof6.052±0.007 hours.[22][20] 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][23][24][a]
Alightcurve 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.[25]
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 800 km and a relatively slow speed of 8.6 km/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.[26] This was the first of two planned asteroid flybys performed by the probe, the second being to the much larger 21 Lutetia in 2010.[27] 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.[28]
^ abLightcurve 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.
^ abcdMainzer, 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: EAR-A-COMPIL-5-NEOWISEDIAM-V1.0. Bibcode:2016PDSS..247.....M. Retrieved 31 August 2018.
^Belskaya, I. N.; Fornasier, S.; Tozzi, G. P.; Gil-Hutton, R.; Cellino, A.; Antonyuk, K.; et al. (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.
^ abWeissman, 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.
^"Target: Steins". IAU–Working Group for Planetary System Nomenclature (WGPSN). Archived from the original on 3 October 2018. Retrieved 14 September 2015.
^Küppers, M.; Mottola, S.; Lowry, S. C.; A'Hearn, M. F.; Barbieri, C.; Barucci, M. A.; et al. (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. S2CID14097820.
^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.
