1558 Järnefelt

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1558 Järnefelt
Discovery [1]
Discovered byL. Oterma
Discovery siteTurku Obs.
Discovery date20 January 1942
MPC designation(1558) Järnefelt
Named after
Gustaf Järnefelt [2][3]
(Finnish astronomer)
1942 BD · 1929 WD1
1934 VX · 1937 EF
1943 GQ · 1951 RC2
1972 BO · A913 AA
main-belt · (outer)[1]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc104.22 yr (38,068 days)
Aphelion3.3244 AU
Perihelion3.1208 AU
3.2226 AU
5.79 yr (2,113 days)
0° 10m 13.44s / day
Physical characteristics
Dimensions54.98±0.56 km[4]
61.77±0.70 km[5]
65.05 km (derived)[6]
65.09±7.1 km (IRAS:6)[7]
18.22±0.06 h[8]
0.0317 (derived)[6]
0.0347±0.009 (IRAS:6)[7]
10.2[4][5][7] · 10.28±0.36[9] · 10.3[1][6]

1558 Järnefelt, provisional designation 1942 BD, is a carbonaceous asteroid from the outer region of the asteroid belt, approximately 65 kilometers in diameter.

It was discovered on 20 January 1942, by Finnish astronomer Liisi Oterma at Turku Observatory in Southwest Finland, and later named for Finnish astronomer Gustaf Järnefelt (1901–1989).[2][10]

Classification and orbit[edit]

The dark C-type asteroid is not a member of any known asteroid family. It orbits the Sun in the outer main-belt at a distance of 3.1–3.3 AU once every 5 years and 9 months (2,113 days). Its orbit has an eccentricity of 0.03 and an inclination of 10° with respect to the ecliptic.[1] Järnefelt was first identified as A913 AA at Heidelberg in 1913. Its first used observation was made at Johannesburg Observatory in 1934, extending the body's observation arc by 8 years prior to its official discovery observation.[10]


In May 2007, a fragmentary rotational lightcurve of Järnefelt was obtained from photometric observations at the U.S. Oakley Observatory, Indiana. It gave a rotation period of 18.22 hours with a brightness variation of 0.40 in magnitude. This was the first time the asteroid's period had been measured. However, the lightcurve is not fully covered by the 90 data points obtained, so the period may be wrong by about 30 percent (U=2).[6][8]

Diameter and albedo[edit]

According to the space-based surveys carried out by the Infrared Astronomical Satellite (IRAS), the Japanese Akari satellite, and NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, the asteroid has an albedo of 0.034 to 0.049, and an estimated diameter between 55.0 and 65.1 kilometers.[4][5][7] The Collaborative Asteroid Lightcurve Link agrees with the data obtained by IRAS and derives an albedo of 0.032 and a diameter of 65.1 kilometers, based on an absolute magnitude of 10.3.[6]


This minor planet was named after Gustaf J. Järnefelt (1901–1989), a Finnish mathematician and astronomer, who was the director of the Helsinki University Observatory and professor of astronomy at the University of Helsinki from 1945 until 1969, when he was succeeded by Paul Kustaanheimo (see 1559 Kustaanheimo). His research included the theory of relativity and the publication artificial satellite observations.[2][3] The official naming citation was published by the Minor Planet Center on 20 February 1976 (M.P.C. 3930).[11]


  1. ^ a b c d e "JPL Small-Body Database Browser: 1558 Jarnefelt (1942 BD)" (2017-03-30 last obs.). Jet Propulsion Laboratory. Retrieved 30 June 2017.
  2. ^ a b c Schmadel, Lutz D. (2007). "(1558) Järnefelt". Dictionary of Minor Planet Names – (1558) Järnefelt. Springer Berlin Heidelberg. p. 123. doi:10.1007/978-3-540-29925-7_1559. ISBN 978-3-540-00238-3.
  3. ^ a b Hannu Karttunen. "Observatory museum Biographies: 1900s — Järnefelt, Gustaf Juhana (1901–1989)". University of Helsinky. Archived from the original on 16 June 2011.
  4. ^ a b c d Masiero, Joseph R.; Mainzer, A. K.; Grav, T.; Bauer, J. M.; Cutri, R. M.; Nugent, C.; et al. (November 2012). "Preliminary Analysis of WISE/NEOWISE 3-Band Cryogenic and Post-cryogenic Observations of Main Belt Asteroids". The Astrophysical Journal Letters. 759 (1): 5. arXiv:1209.5794. Bibcode:2012ApJ...759L...8M. doi:10.1088/2041-8205/759/1/L8. Retrieved 25 May 2016.
  5. ^ 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. Retrieved 17 October 2019. (online, AcuA catalog p. 153)
  6. ^ a b c d e f "LCDB Data for (1558) Jarnefelt". Asteroid Lightcurve Database (LCDB). Retrieved 25 May 2016.
  7. ^ a b c d Tedesco, E. F.; Noah, P. V.; Noah, M.; Price, S. D. (October 2004). "IRAS Minor Planet Survey V6.0". NASA Planetary Data System – IRAS-A-FPA-3-RDR-IMPS-V6.0. Bibcode:2004PDSS...12.....T. Retrieved 17 October 2019.
  8. ^ a b Hawkins, Scot; Ditteon, Richard (March 2008). "Asteroid Lightcurve Analysis at the Oakley Observatory - May 2007". The Minor Planet Bulletin. 35 (1): 1–4. Bibcode:2008MPBu...35....1H. ISSN 1052-8091. Retrieved 25 May 2016.
  9. ^ 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 25 May 2016.
  10. ^ a b "1558 Jarnefelt (1942 BD)". Minor Planet Center. Retrieved 25 May 2016.
  11. ^ 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.

External links[edit]