1200 Imperatrix

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1200 Imperatrix
Discovery [1]
Discovered by K. Reinmuth
Discovery site Heidelberg Obs.
Discovery date 14 September 1931
MPC designation (1200) Imperatrix
Named after
empress (in Latin)[2]
1931 RH · 1929 CX
1950 DC1 · 1957 OY
A913 EC · A915 TL
A924 GC
main-belt · (outer)[3]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc 101.75 yr (37,165 days)
Aphelion 3.3873 AU
Perihelion 2.7436 AU
3.0654 AU
Eccentricity 0.1050
5.37 yr (1,960 days)
0° 11m 0.96s / day
Inclination 4.5935°
Physical characteristics
Dimensions 36.00±0.42 km[5]
37.36±9.71 km[6]
39.39 km (derived)[3]
39.52±3.9 km[7]
42.006±0.390 km[8]
42.777±0.309 km[9]
43.64±0.61 km[10]
13.34±0.11 h[11]
17.769±0.002 h[12]
0.0545 (derived)[3]
C (assumed)[3]
10.50[7][9][10] · 10.74±0.28[13] · 10.80[3][5] · 10.9[1] · 10.91[6]

1200 Imperatrix, provisional designation 1931 RH, is a carbonaceous Hygiean asteroid from the outer regions of the asteroid belt, approximately 40 kilometers in diameter. It was discovered by German astronomer Karl Reinmuth at the Heidelberg-Königstuhl State Observatory on 14 September 1931.[14] The asteroid was named after the Latin word for empress.

Orbit and classification[edit]

Imperatrix is a member of the Hygiea family (601),[4] a very large asteroid family named after 10 Hygiea, the main belt's fourth-largest asteroid. Imperatrix orbits the Sun in the outer main-belt at a distance of 2.7–3.4 AU once every 5 years and 4 months (1,960 days). Its orbit has an eccentricity of 0.11 and an inclination of 5° with respect to the ecliptic.[1]

The body's observation arc begins with its first identification as A913 EC at Simeiz Observatory in March 1913, more than 18 years prior to its official discovery observation at Heidelberg.[14]

Physical characteristics[edit]

Imperatrix is an assumed C-type asteroid which is also the overall spectral type of the Hygiea family.[3][15]:23

Rotation period[edit]

In in August 2000, a rotational lightcurve of Imperatrix was obtained from photometric observations at the River Oaks Observatory (915) in Texas. Lightcurve analysis gave a rotation period of 13.34 hours with a brightness variation of 0.23 magnitude (U=2).[11] In September 2011, photometric observations by French amateur astronomers Pierre Antonini and René Roy gave a refined period of 17.769 hours with an amplitude of 0.21 magnitude (U=3).[12]

Diameter and albedo[edit]

According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the Japanese Akari satellite and the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Imperatrix measures between 36.00 and 43.64 kilometers in diameter and its surface has an albedo between 0.04 and 0.0714.[5][6][7][8][9][10]

The Collaborative Asteroid Lightcurve Link derives an albedo of 0.0545 and a diameter of 39.39 kilometers based on an absolute magnitude of 10.8.[3]


This minor planet was named "Imperatrix", which is Latin for empress. The naming was proposed by German ARI-astronomer Gustav Stracke, after whom 1019 Strackea was named. Any specific reference to an occurrence or person is unknown, according to the author of the Dictionary of Minor Planets, Lutz Schmadel and his communications with Ingrid van Houten-Groeneveld, who also worked at Heidelberg).[2]


  1. ^ a b c d "JPL Small-Body Database Browser: 1200 Imperatrix (1931 RH)" (2017-07-03 last obs.). Jet Propulsion Laboratory. Retrieved 26 September 2017. 
  2. ^ a b Schmadel, Lutz D. (2007). Dictionary of Minor Planet Names – (1200) Imperatrix. Springer Berlin Heidelberg. p. 100. ISBN 978-3-540-00238-3. Retrieved 26 September 2017. 
  3. ^ a b c d e f g "LCDB Data for (1200) Imperatrix". Asteroid Lightcurve Database (LCDB). Retrieved 26 September 2017. 
  4. ^ a b "Small Bodies Data Ferret". Nesvorny HCM Asteroid Families V3.0. Retrieved 26 September 2017. 
  5. ^ a b c d e 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:1209.5794Freely accessible. Bibcode:2012ApJ...759L...8M. doi:10.1088/2041-8205/759/1/L8. Retrieved 26 September 2017. 
  6. ^ 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:1606.08923Freely accessible. Bibcode:2016AJ....152...63N. doi:10.3847/0004-6256/152/3/63. Retrieved 26 September 2017. 
  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. Bibcode:2004PDSS...12.....T. Retrieved 26 September 2017. 
  8. ^ a b 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:1406.6645Freely accessible. Bibcode:2014ApJ...791..121M. doi:10.1088/0004-637X/791/2/121. Retrieved 26 September 2017. 
  9. ^ a b c d Mainzer, A.; Grav, T.; Masiero, J.; Hand, E.; Bauer, J.; Tholen, D.; et al. (November 2011). "NEOWISE Studies of Spectrophotometrically Classified Asteroids: Preliminary Results" (PDF). The Astrophysical Journal. 741 (2): 25. arXiv:1109.6407Freely accessible. Bibcode:2011ApJ...741...90M. doi:10.1088/0004-637X/741/2/90. Retrieved 26 September 2017. 
  10. ^ 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 26 September 2017. 
  11. ^ a b Holliday, B. (March 2001). "Photometry of Asteroid 191 Kolga and 1200 Imperatrix". The Minor Planet Bulletin. 28: 13. Bibcode:2001MPBu...28...13H. Retrieved 26 September 2017. 
  12. ^ a b Behrend, Raoul. "Asteroids and comets rotation curves – (1200) Imperatrix". Geneva Observatory. Retrieved 26 September 2017. 
  13. ^ 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:1506.00762Freely accessible. Bibcode:2015Icar..261...34V. doi:10.1016/j.icarus.2015.08.007. Retrieved 26 September 2017. 
  14. ^ a b "1200 Imperatrix (1931 RH)". Minor Planet Center. Retrieved 26 September 2017. 
  15. ^ Nesvorný, D.; Broz, M.; Carruba, V. (December 2014). "Identification and Dynamical Properties of Asteroid Families" (PDF). Asteroids IV: 297–321. arXiv:1502.01628Freely accessible. Bibcode:2015aste.book..297N. doi:10.2458/azu_uapress_9780816532131-ch016. Retrieved 26 September 2017. 

External links[edit]