1656 Suomi

1656 Suomi (prov. designation: 1942 EC) is a binary Hungaria asteroid and sizable Mars-crosser from the innermost regions of the asteroid belt. It was discovered on 11 March 1942, by Finnish astronomer Yrjö Väisälä at Turku Observatory in Southwest Finland,[3] who named it "Suomi", the native name of Finland.[2] The stony asteroid has a short rotation period of 2.6 hours and measures approximately 7.9 kilometers in diameter. In June 2020, a companion was discovered by Brian Warner, Robert Stephens and Alan Harris.[6] The satellite measures more than 1.98 kilometers in diameter, about 26% of the primary, which it orbits once every 57.9 hours at an average distance of 30 kilometers.[4][5]

1656 Suomi
Discovery[1]
Discovered byY. Väisälä
Discovery siteTurku Obs.
Discovery date11 March 1942
Designations
(1656) Suomi
Named after
Finland (country)[2]
1942 EC · 1955 HL
Mars-crosser[1] · Hungaria[3]
binary
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc75.24 years (27,480 days)
Aphelion2.1093 AU
Perihelion1.6456 AU
1.8774 AU
Eccentricity0.1235
2.57 yr (940 days)
174.69°
0° 22m 59.16s / day
Inclination25.067°
175.57°
287.44°
Known satellites1 1.98+ km (> 0.26Ds/Dp; P: 57.92 h)[4][5][6]
Earth MOID0.7551 AU
Physical characteristics
Mean diameter
7.86±0.7 km (IRAS:3)[7]
7.9 km[8]
2.42±0.02 h[8]
2.583±0.004 h[9]
2.5879±0.0002 h[10]
2.5879±0.0003 h[11]
2.59±0.01 h[12][13][14]
62.16 h (wrong)[15]
0.1556±0.032 (IRAS:3)[7]
0.157[8]
Tholen = S[1] · S[16][5]
12.9[1][17] · 12.97±0.31[18] · 13.13±0.11[8] · 13.146±0.1[5][19] · 13.16[7]

    Orbit and classification

    Suomi is a member of the Hungaria family, which form the innermost dense concentration of asteroids in the Solar System. It orbits the Sun at a distance of 1.6–2.1 AU once every 2 years and 7 months (940 days). Its orbit has an eccentricity of 0.12 and an inclination of 25° with respect to the ecliptic.[1]

    It is also classified as a Mars-crossing asteroid, since its perihelion – the point in its orbit, where it is nearest to the Sun – is less than the average orbital distance of the planet Mars (1.666 AU). Suomi's observation arc begins on the preceding night of its discovery, with an observation taken at Johannesburg Observatory on 10 March 1942.[3]

    Naming

    As with 1453 Fennia, this minor planet was named after Finland (Finnish: Suomi).[2] The official naming citation was published by the Minor Planet Center on 20 February 1976 (M.P.C. 3932).[20]

    Physical characteristics

    In the Tholen taxonomy, Suomi is a stony S-type asteroid.[1]

    Diameter and albedo

    According to the survey carried out by the Infrared Astronomical Satellite IRAS, Suomi measures 7.86 kilometers in diameter and its surface has an albedo of 0.156,[7] making it one of the largest Mars crossing asteroid with a known diameter.[21] The Collaborative Asteroid Lightcurve Link (CALL) agrees with IRAS, and adopts an albedo of 0.157 and a diameter of 7.9 kilometers with an absolute magnitude of 13.146.[5]

    Rotation period

    Since 1991, a large number of rotational lightcurves of Suomi have been obtained from photometric observations (also see infobox). CALL adopts a rotation period of 2.583 hours with a brightness variation of 0.20 magnitude (U=3).[5]

    References
    1. "JPL Small-Body Database Browser: 1656 Suomi (1942 EC)" (2017-06-06 last obs.). Jet Propulsion Laboratory. Retrieved 30 June 2017.
    2. Schmadel, Lutz D. (2007). "(1656) Suomi". Dictionary of Minor Planet Names. Springer Berlin Heidelberg. p. 132. doi:10.1007/978-3-540-29925-7_1657. ISBN 978-3-540-00238-3.
    3. "1656 Suomi (1942 EC)". Minor Planet Center. Retrieved 24 December 2016.
    4. Johnston, Robert (11 October 2020). "(1656) Suomi". johnstonsarchive.net. Retrieved 24 October 2020.
    5. "LCDB Data for (1656) Suomi". Asteroid Lightcurve Database (LCDB). Retrieved 24 December 2016.
    6. Warner, Brian D.; Stephens, Robert D.; Harris, Alan W. (October 2020). "Binary Asteroids at the Center for Solar System Studies" (PDF). Minor Planet Bulletin. 47 (4): 305–308. Bibcode:2020MPBu...47..305W. ISSN 1052-8091.
    7. Tedesco, E. F.; Noah, P. V.; Noah, M.; Price, S. D. (October 2004). "IRAS Minor Planet Survey V6.0". NASA Planetary Data System. 12: IRAS-A-FPA-3-RDR-IMPS-V6.0. Bibcode:2004PDSS...12.....T. Retrieved 22 October 2019.
    8. 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 24 December 2016.
    9. Warner, Brian D. (July 2009). "Asteroid Lightcurve Analysis at the Palmer Divide Observatory: 2008 December - 2009 March". The Minor Planet Bulletin. 36 (3): 109–116. Bibcode:2009MPBu...36..109W. ISSN 1052-8091. Retrieved 24 December 2016.
    10. Warner, Brian D. (October 2012). "Asteroid Lightcurve Analysis at the Palmer Divide Observatory: 2012 March - June". The Minor Planet Bulletin. 39 (4): 245–252. Bibcode:2012MPBu...39..245W. ISSN 1052-8091. Retrieved 24 December 2016.
    11. Warner, Brian D. (January 2016). "Asteroid Lightcurve Analysis at CS3-Palmer Divide Station: 2015 June-September". The Minor Planet Bulletin. 43 (1): 57–65. Bibcode:2016MPBu...43...57W. ISSN 1052-8091. Retrieved 24 December 2016.
    12. Stephens, Robert D. (December 2004). "Photometry of 1196 Sheba, 1341 Edmee, 1656 Suomi, 2577 Litva, and 2612 Kathryn". The Minor Planet Bulletin. 31 (4): 95–97. Bibcode:2004MPBu...31...95S. ISSN 1052-8091. Retrieved 24 December 2016.
    13. Brinsfield, James W. (March 2008). "The Rotation Periods of 1465 Autonoma, 1656 Suomi 4483 Petofi, 4853 Marielukac, and (85275) 1994 LY". The Minor Planet Bulletin. 35 (1): 23–24. Bibcode:2008MPBu...35...23B. ISSN 1052-8091. Retrieved 24 December 2016.
    14. Warner, Brian D. (July 2014). "Asteroid Lightcurve Analysis at CS3-Palmer Divide Station: 2014 January-March". The Minor Planet Bulletin. 41 (3): 144–155. Bibcode:2014MPBu...41..144W. ISSN 1052-8091. Retrieved 24 December 2016.
    15. Behrend, Raoul. "Asteroids and comets rotation curves – (1656) Suomi". Geneva Observatory. Retrieved 24 December 2016.
    16. Sanchez, Juan A.; Michelsen, René; Reddy, Vishnu; Nathues, Andreas (July 2013). "Surface composition and taxonomic classification of a group of near-Earth and Mars-crossing asteroids". Icarus. 225 (1): 131–140. arXiv:1302.4449. Bibcode:2013Icar..225..131S. CiteSeerX 10.1.1.743.8700. doi:10.1016/j.icarus.2013.02.036. Retrieved 24 December 2016.
    17. Faure, Gerard; Garret, Lawrence (December 2007). "Suggested Revised H Values of Selected Asteroids: Report Number 3". The Minor Planet Bulletin. 34 (4): 95–99. Bibcode:2007MPBu...34...95F. ISSN 1052-8091. Retrieved 24 December 2016.
    18. 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 24 December 2016.
    19. 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 24 December 2016.
    20. 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.
    21. "JPL Small-Body Database Search Engine: orbital class (MCA) and diameter > 0 (km)". JPL Solar System Dynamics. Retrieved 26 May 2015.
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