# 2867 Šteins

Discovery[1] Contrast-enhanced image of Šteins by Rosetta Nikolai Stepanovich Chernykh Crimean Astrophysical Observatory 4 November 1969 (2867) Šteins Kārlis Šteins 1969 VC Main belt Epoch 13 January 2016 (JD 2457400.5) Uncertainty parameter 0 64.29 yr (23481 days) 2.7074 AU (405.02 Gm) 2.01961 AU (302.129 Gm) 2.36349 AU (353.573 Gm) 0.14550 3.63 yr (1327.2 d) 325.187° 0° 16m 16.5s / day 9.9348° 55.371° 251.16° 6.67 × 5.81 × 4.47 km[4] 2.65 km[5] 6.049 h (0.2520 d) 6.05 h 0.34 ± 0.06 E 12.5

2867 Šteins is a small main-belt asteroid that was discovered in 1969 by Nikolai Chernykh.[1] It is named after Kārlis Šteins, a Latvian and Soviet astronomer.[6] Šteins was visited by the European Space Agency's Rosetta space probe in 2008.

## 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 km.[7] Studying the asteroid before its flyby, the ESA Rosetta space probe showed via a lightcurve analysis that Šteins has a rotation period of about six hours, is irregular in shape, and does not have any moons.[8]

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 a large crater (2.1 km diameter), which surprised scientists, who were at first amazed the asteroid survived such an impact,[9] while later it turned out that the ratio of crater diameter ${\displaystyle D}$ to asteroid size ${\displaystyle R}$ is with a value of ${\displaystyle D/R=0.79}$ in fact not abnormally large.[10] The photographs of Šteins taken by Rosetta allowed scientists to determine that the asteroid has dimensions of 6.67 × 5.81 × 4.47 km,[4] which equates to a mean diameter of 5.3 km.[5]

## Flyby

On September 5, 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,[11] this was the first of two planned asteroid flybys performed by the probe, the second being to the much larger 21 Lutetia in 2010.[12] 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.[13]

## Nomenclature

On May 11, 2012, the Working Group for Planetary System Nomenclature announced a naming system for geographical features on Šteins.[14] Inspired by the asteroid's gem-like shape, its craters are given the English-language names of precious stones, with the largest being named Diamond. Except for the montes of Mercury and the lunar maria, the craters of Šteins are the only features in the solar system whose names are not derived from proper nouns.[15] In addition, a distinct region on the asteroid has been named Chernykh Regio after the discoverer.[16]

## References

1. ^ a b "Discovery Circumstances: Numbered Minor Planets (1)-(5000)". IAU: Minor Planet Center. Archived from the original on 2 February 2009. Retrieved December 29, 2008.
2. ^
3. ^ "2867 Steins (1969 VC)". JPL Small-Body Database. NASA/Jet Propulsion Laboratory. Retrieved 15 April 2016.
4. ^ a b "Rosetta's OSIRIS cameras reveal the nature of asteroid Steins". ESA Science & Technology. January 8, 2010.
5. ^ a b
6. ^ Schmadel, Lutz (2003). Dictionary of minor planet names (fifth ed.). Germany: Springer. p. 235. ISBN 3-540-00238-3. Retrieved 2008-12-29.
7. ^ S. Fornasier; I. Belskaya; M. Fulchignoni; M. A. Barucci; C. Barbieri (2006). "First albedo determination of 2867 Steins, target of the Rosetta mission". Astronomy & Astrophysics. 449 (2): L9–L12. arXiv:. Bibcode:2006A&A...449L...9F. doi:10.1051/0004-6361:20064913.
8. ^ Michael Küppers; Uwe Keller; Rita Schulz; Gerhard Schwehm. "OSIRIS camera on Rosetta obtains 'light curve' of asteroid Steins".
9. ^ "Steins: A diamond in the sky". ESA Rosetta News. Retrieved 2009-05-29.
10. ^ Burchell, M.J.; Leliwa-Kopystynski, J. (December 2010). "The large crater on the small Asteroid (2867) Steins". Icarus. 210 (2): 707–712. Bibcode:2010Icar..210..707B. doi:10.1016/j.icarus.2010.07.026.
11. ^ "Encounter of a different kind: Rosetta observes asteroid at close quarters". ESA Rosetta News. Archived from the original on 10 May 2009. Retrieved 2009-05-29.
12. ^ 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.
13. ^ Talevi, Monica (September 4, 2008). "Rosetta Steins fly-by timeline". European Space Agency. Retrieved 2008-09-05.
14. ^ "First Names Approved for Asteroid (2867) Steins". USGS–Astrogeology Science Center. Retrieved 14 September 2015.
15. ^ "Gazetteer of Planetary Nomenclature–Categories for Naming Features on Planets and Satellites". IAU–Working Group for Planetary System Nomenclature (WGPSN). Retrieved 14 September 2015.
16. ^ "Target: Steins". IAU–Working Group for Planetary System Nomenclature (WGPSN). Retrieved 14 September 2015.