Discovered by L. Oterma MPC designation 1558 Järnefelt Discovered 20 January 1942 Orbits Sun Discovery site Iso-Heikkilä Observatory | Discovery date 20 January 1942 Minor planet category main-belt · (outer) Absolute magnitude 10.2 Asteroid group Asteroid belt | |
Named after Gustaf Järnefelt(astronomer) Alternative names 1942 BD · 1929 WD11934 VX · 1937 EF1943 GQ · 1951 RC21972 BO · A913 AA People also search for 1680 Per Brahe, Sun, 2268 Szmytowna | ||
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.
The dark C-type asteroid orbits the Sun 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. 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.
In May 2007, a fragmentary rotational light-curve of Järnefelt was obtained from photometric observations at the U.S. Oakley Observatory, Indiana. It gave a rotation period of 7001182200000000000♠18.22±0.06 hours with a brightness variation of 0.40 in magnitude. This was the first time the asteroid's period had been measured. However, the light-curve is not fully covered by the 90 data points obtained, so the period may be wrong by about 30 percent (U=2).
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. 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.
The minor planet was named after Finnish astronomer and director of the Helsinki University Observatory in the post-war period, Gustaf Järnefelt (1901–1989). His research included the theory of relativity and the publication artificial satellite observations. Naming citation was published before November 1977 (M.P.C. 3930).