| Discovery[1] | |
|---|---|
| Discovered by | E. L. Johnson |
| Discovery site | Union Obs. |
| Discovery date | 7 September 1947 |
| Designations | |
| (1585) Union | |
Named after | Union Observatory (aka Johannesburg Obs.)[2] |
| 1947 RG · 1929 DB 1937 QF · 1939 CD1 1944 DG · 1949 EE 1952 QA1 · 1952 SD | |
| main-belt · (outer)[3] | |
| Orbital characteristics[1] | |
| Epoch 4 September 2017 (JD 2458000.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 78.37 yr (28,624 days) |
| Aphelion | 3.8332AU |
| Perihelion | 2.0231 AU |
| 2.9281 AU | |
| Eccentricity | 0.3091 |
| 5.01yr (1,830 days) | |
| 304.39° | |
| 0° 11m 48.12s / day | |
| Inclination | 26.187° |
| 150.10° | |
| 264.54° | |
| Physical characteristics | |
| Dimensions | 49.01±18.07 km[4] 50.42±1.6 km[3][5] 50.68±0.88 km[6] 55.271±0.243 km[7] 55.42±18.20 km[8] 56.014±0.292 km[9] |
| 9.38h[10] 24 h(fragmentary)[11] | |
| 0.0304±0.0028[9] 0.031±0.004[7] 0.0378±0.003[3][5] 0.038±0.001[6] 0.04±0.04[8] 0.05±0.02[4] | |
| P[9] · C[3] B–V = 0.590[1] U–B = 0.290[1] | |
| 10.33±0.22[12] · 10.35[8] · 10.66[1][4][5][6] · 10.67[3][9][10] | |
1585 Union, provisional designation1947 RG, is a dark backgroundasteroid from the outer regions of theasteroid belt, approximately 52 kilometers in diameter. It was discovered on 7 September 1947, by South African astronomerErnest Johnson at theUnion Observatory in Johannesburg, South Africa.[13] The asteroid was named after the discovering observatory.[2]
Union is not a member of any knownasteroid family. It orbits the Sun in theouter main belt at a distance of 2.0–3.8 AU once every 5.01 years (1,830 days). Its orbit has aneccentricity of 0.31 and aninclination of 26° with respect to theecliptic.[1]
In 1929, the asteroid was first identified as1929 DB at theUccle Observatory in Belgium. The body'sobservation arc begins at the FinnishTurku Observatory in February 1939, more than 17 years prior to its official discovery observation at Johannesburg.[13]
Union has been characterized as aP-type asteroid by theWide-field Infrared Survey Explorer (WISE), while the LCDB assumes a generic carbonaceousC-type.[3][9]
In March 1984, a rotationallightcurve ofUnion was obtained from photometric observations by American astronomerRichard Binzel. Lightcurve analysis gave arotation period of 9.38 hours with a brightness variation of 0.22magnitude (U=2).[10] In addition, a fragmentary lightcurve with a period of 24 hours was obtained by French amateur astronomerLaurent Bernasconi in 2004 (U=1).[11]
According to the surveys carried out by the Infrared Astronomical SatelliteIRAS, the JapaneseAkari satellite and theNEOWISE mission of NASA's WISE telescope,Union measures between 49.01 and 56.014 kilometers in diameter and its surface has analbedo between 0.0304 and 0.05.[4][5][6][7][8][9]
TheCollaborative Asteroid Lightcurve Link adopt the results obtained by IRAS, that is, an albedo of 0.0378 and a diameter of 50.42 kilometers. CALL also takes anabsolute magnitude of 10.67 from Richard Binzel.[3]
Thisminor planet was named after the discovering Union Observatory, also known as theJohannesburg Observatory, Transvaal Observatory (1909–1912) and Republic Observatory (1961–1971). The officialnaming citation was published by theMinor Planet Center in June 1953 (M.P.C. 941).[14]
