(1585) Union

1585 Union
Discovered byE. L. Johnson
Discovery siteUnion Obs.
Discovery date7 September 1947
(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 arc78.37 yr (28,624 days)
Aphelion3.8332 AU
Perihelion2.0231 AU
2.9281 AU
5.01 yr (1,830 days)
0° 11m 48.12s / day
Physical characteristics
Dimensions49.01±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]
9.38 h[10]
24 h (fragmentary)[11]
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 designation 1947 RG, is a dark background asteroid from the outer regions of the asteroid belt, approximately 52 kilometers in diameter. It was discovered on 7 September 1947, by South African astronomer Ernest Johnson at the Union Observatory in Johannesburg, South Africa.[13] The asteroid was named after the discovering observatory.[2]

Orbit and classification[]

Union is not a member of any known asteroid family. It orbits the Sun in the outer main belt at a distance of 2.0–3.8 AU once every 5.01 years (1,830 days). Its orbit has an eccentricity of 0.31 and an inclination of 26° with respect to the ecliptic.[1]

In 1929, the asteroid was first identified as 1929 DB at the Uccle Observatory in Belgium. The body's observation arc begins at the Finnish Turku Observatory in February 1939, more than 17 years prior to its official discovery observation at Johannesburg.[13]

Physical characteristics[]

Union has been characterized as a P-type asteroid by the Wide-field Infrared Survey Explorer (WISE), while the LCDB assumes a generic carbonaceous C-type.[3][9]

Rotation period[]

In March 1984, a rotational lightcurve of Union was obtained from photometric observations by American astronomer Richard Binzel. Lightcurve analysis gave a rotation period of 9.38 hours with a brightness variation of 0.22 magnitude (U=2).[10] In addition, a fragmentary lightcurve with a period of 24 hours was obtained by French amateur astronomer Laurent Bernasconi in 2004 (U=1).[11]

Diameter and albedo[]

According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the Japanese Akari satellite and the NEOWISE mission of NASA's WISE telescope, Union measures between 49.01 and 56.014 kilometers in diameter and its surface has an albedo between 0.0304 and 0.05.[4][5][6][7][8][9]

The Collaborative 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 an absolute magnitude of 10.67 from Richard Binzel.[3]


This minor planet was named after the discovering Union Observatory, also known as the Johannesburg Observatory, Transvaal Observatory (1909–1912) and Republic Observatory (1961–1971). The official naming citation was published by the Minor Planet Center in June 1953 (M.P.C. 941).[14]


  1. ^ a b c d e f "JPL Small-Body Database Browser: 1585 Union (1947 RG)" (2017-07-05 last obs.). Jet Propulsion Laboratory. Retrieved 30 August 2017.
  2. ^ a b Schmadel, Lutz D. (2007). "(1585) Union". Dictionary of Minor Planet Names – (1585) Union. Springer Berlin Heidelberg. p. 125. doi:10.1007/978-3-540-29925-7_1586. ISBN 978-3-540-00238-3.
  3. ^ a b c d e f g "LCDB Data for (1585) Union". Asteroid Lightcurve Database (LCDB). Retrieved 30 August 2017.
  4. ^ a b c d Nugent, C. R.; Mainzer, A.; Masiero, J.; Bauer, J.; Cutri, R. M.; Grav, T.; et al. (December 2015). "NEOWISE Reactivation Mission Year One: Preliminary Asteroid Diameters and Albedos". The Astrophysical Journal. 814 (2): 13. arXiv:1509.02522. Bibcode:2015ApJ...814..117N. doi:10.1088/0004-637X/814/2/117. Retrieved 30 August 2017.
  5. ^ 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.
  6. ^ 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. (online, AcuA catalog p. 153)
  7. ^ a b c Masiero, Joseph R.; Grav, T.; Mainzer, A. K.; Nugent, C. R.; Bauer, J. M.; Stevenson, R.; et al. (August 2014). "Main-belt Asteroids with WISE/NEOWISE: Near-infrared Albedos". The Astrophysical Journal. 791 (2): 11. arXiv:1406.6645. Bibcode:2014ApJ...791..121M. doi:10.1088/0004-637X/791/2/121. Retrieved 30 August 2017.
  8. ^ a b c d Nugent, C. R.; Mainzer, A.; Bauer, J.; Cutri, R. M.; Kramer, E. A.; Grav, T.; et al. (September 2016). "NEOWISE Reactivation Mission Year Two: Asteroid Diameters and Albedos". The Astronomical Journal. 152 (3): 12. arXiv:1606.08923. Bibcode:2016AJ....152...63N. doi:10.3847/0004-6256/152/3/63. Retrieved 30 August 2017.
  9. ^ a b c d e f Mainzer, A.; Grav, T.; Masiero, J.; Hand, E.; Bauer, J.; Tholen, D.; et al. (November 2011). "NEOWISE Studies of Spectrophotometrically Classified Asteroids: Preliminary Results". The Astrophysical Journal. 741 (2): 25. arXiv:1109.6407. Bibcode:2011ApJ...741...90M. doi:10.1088/0004-637X/741/2/90.
  10. ^ a b c Binzel, R. P. (October 1987). "A photoelectric survey of 130 asteroids". Icarus. 72 (1): 135–208. Bibcode:1987Icar...72..135B. doi:10.1016/0019-1035(87)90125-4. ISSN 0019-1035. Retrieved 30 August 2017.
  11. ^ a b Behrend, Raoul. "Asteroids and comets rotation curves – (1585) Union". Geneva Observatory. Retrieved 30 August 2017.
  12. ^ 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 30 August 2017.
  13. ^ a b "1585 Union (1947 RG)". Minor Planet Center. Retrieved 30 August 2017.
  14. ^ Schmadel, Lutz D. (2009). "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[]