| Discovery[1] | |
|---|---|
| Discovered by | L. Oterma |
| Discovery site | Turku Obs. |
| Discovery date | 20 January 1942 |
| Designations | |
| (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 arc | 104.22 yr (38,068 days) |
| Aphelion | 3.3244AU |
| Perihelion | 3.1208 AU |
| 3.2226 AU | |
| Eccentricity | 0.0316 |
| 5.79yr (2,113 days) | |
| 105.25° | |
| 0° 10m 13.44s / day | |
| Inclination | 10.489° |
| 110.93° | |
| 291.23° | |
| Physical characteristics | |
| Dimensions | 54.98±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±0.06h[8] | |
| 0.0317(derived)[6] 0.0347±0.009(IRAS:6)[7] 0.039±0.001[5] 0.049±0.008[4] | |
| C[6] | |
| 10.2[4][5][7] · 10.28±0.36[9] · 10.3[1][6] | |
1558 Järnefelt (provisional designation1942 BD) is a carbonaceousasteroid from the outer region of theasteroid belt, approximately 65 kilometers in diameter. It was discovered on 20 January 1942, by Finnish astronomerLiisi Oterma atTurku Observatory in Southwest Finland, and later named for Finnish astronomerGustaf Järnefelt (1901–1989).[2][10]
The darkC-type asteroid is not a member of any knownasteroid family. It orbits the Sun in theouter main-belt at a distance of 3.1–3.3 AU once every 5 years and 9 months (2,113 days). Its orbit has aneccentricity of 0.03 and aninclination of 10° with respect to theecliptic.[1] Järnefelt was first identified asA913 AA atHeidelberg in 1913. Its first used observation was made atJohannesburg Observatory in 1934, extending the body'sobservation arc by 8 years prior to its official discovery observation.[10]
In May 2007, a fragmentary rotationallightcurve of Järnefelt was obtained from photometric observations at the U.S.Oakley Observatory, Indiana. It gave arotation period of18.22 hours with a brightness variation of 0.40 inmagnitude. 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]
According to the space-based surveys carried out by the Infrared Astronomical Satellite (IRAS), the JapaneseAkari satellite, and NASA'sWide-field Infrared Survey Explorer with its subsequentNEOWISE mission, the asteroid has analbedo of 0.034 to 0.049, and an estimated diameter between 55.0 and 65.1 kilometers.[4][5][7] TheCollaborative 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 anabsolute magnitude of 10.3.[6]
Thisminor planet was named after Gustaf J. Järnefelt (1901–1989), a Finnish mathematician and astronomer, who was the director of theHelsinki University Observatory and professor of astronomy at theUniversity of Helsinki from 1945 until 1969, when he was succeeded by Paul Kustaanheimo(see1559 Kustaanheimo). His research included thetheory of relativity and the publication artificial satellite observations.[2][3] The officialnaming citation was published by theMinor Planet Center on 20 February 1976 (M.P.C. 3930).[11]
