1178 Irmela

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1178 Irmela
Discovery [1]
Discovered by M. F. Wolf
Discovery site Heidelberg Obs.
Discovery date 13 March 1931
MPC designation (1178) Irmela
Named after
Irmela Ruska
(wife of Ernst Ruska)[2]
1931 EC · 1940 GC
1962 JD · 1988 CK6
main-belt · (middle)[3]
Orbital characteristics[1]
Epoch 16 February 2017 (JD 2457800.5)
Uncertainty parameter 0
Observation arc 85.83 yr (31,351 days)
Aphelion 3.1700 AU
Perihelion 2.1916 AU
2.6808 AU
Eccentricity 0.1825
4.39 yr (1,603 days)
0° 13m 28.56s / day
Inclination 6.9511°
Physical characteristics
Dimensions 17.00±3.43 km[4]
17.50±4.91 km[5]
17.90±0.57 km[6]
19.05 km (derived)[3]
19.09±0.8 km (IRAS:15)[7]
19.663±0.049 km[8]
20.683±0.181 km[9]
11.989±0.001 h[10]
19.17 h[11]
0.0838 (derived)[3]
0.0916±0.008 (IRAS:15)[7]
11.81[1][4][6][7] · 11.87±0.35[12] · 11.91[3][9][11] · 12.14[5]

1178 Irmela, provisional designation 1931 EC, is a stony asteroid from the middle regions of the asteroid belt, approximately 19 kilometers in diameter.

It was discovered on 13 March 1931, by German astronomer Max Wolf at Heidelberg Observatory in southwest Germany.[13] The asteroid was named after Irmela Ruska, wife of Ernst Ruska.[2]

Orbit and classification[edit]

Irmela orbits the Sun in the central main-belt at a distance of 2.2–3.2 AU once every 4 years and 5 months (1,603 days). Its orbit has an eccentricity of 0.18 and an inclination of 7° with respect to the ecliptic.[1] A first precovery was taken at Lowell Observatory in February 1931, extending the body's observation arc by 3 weeks prior to its official discovery observation at Heidelberg.[13]

Physical characteristics[edit]


In May 1984, a first rotational lightcurve of Irmela was obtained from photometric observations by American astronomer Richard Binzel. Lightcurve analysis gave a rotation period of 19.17 hours with a brightness variation of 0.34 magnitude (U=2).[11]

In March 2010, astronomer Robert Stephens obtained another lightcurve at the Center for Solar System Studies, that gave a divergent period of 11.989 hours with an amplitude of 0.40 magnitude (U=2).[10]

Diameter and albedo[edit]

According to the 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, Irmela measures between 17.00 and 20.683 kilometers in diameter and its surface has an albedo between 0.0503 and 0.105.[4][5][6][7][8][9]

10µm radiometric data collected from Kitt Peak National Observatory in 1975, gave a diameter estimate of 19 kilometers.[14]

The Collaborative Asteroid Lightcurve Link characterizes Irmela as a common S-type asteroid, derives an albedo of 0.0838 and calculates a diameter of 19.05 kilometers with an absolute magnitude of 11.91.[3]


This minor planet was named after Irmela Ruska, wife of the inventor of the electron microscope and 1986 Nobelist, the German physicist Ernst Ruska (1906–1988), who shared the Nobel prize with Gerd Binnig and Heinrich Rohrer. The naming was granted by Max Wolf to his college August Kopff, himself a prolific discoverer of minor planets. The citation was published by Paul Herget in The Names of the Minor Planets (H 109).[2]


  1. ^ a b c d "JPL Small-Body Database Browser: 1178 Irmela (1931 EC)" (2016-12-22 last obs.). Jet Propulsion Laboratory. Retrieved 2 May 2017. 
  2. ^ a b c Schmadel, Lutz D. (2007). Dictionary of Minor Planet Names – (1178) Irmela. Springer Berlin Heidelberg. p. 99. ISBN 978-3-540-00238-3. Retrieved 2 May 2017. 
  3. ^ a b c d e f "LCDB Data for (1178) Irmela". Asteroid Lightcurve Database (LCDB). Retrieved 2 May 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:1509.02522Freely accessible. Bibcode:2015ApJ...814..117N. doi:10.1088/0004-637X/814/2/117. Retrieved 2 May 2017. 
  5. ^ 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 2 May 2017. 
  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. Retrieved 2 May 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 2 May 2017. 
  8. ^ 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:1406.6645Freely accessible. Bibcode:2014ApJ...791..121M. doi:10.1088/0004-637X/791/2/121. Retrieved 2 May 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 2 May 2017. 
  10. ^ a b Stephens, Robert D. (April 2012). "Asteroids Observed from GMARS and Santana Observatories: 2011 October- December". The Minor Planet Bulletin. 39 (2): 80–82. Bibcode:2012MPBu...39...80S. ISSN 1052-8091. Retrieved 2 May 2017. 
  11. ^ a b c Binzel, R. P. (October 1987). "A photoelectric survey of 130 asteroids". Icarus: 135–208. Bibcode:1987Icar...72..135B. doi:10.1016/0019-1035(87)90125-4. ISSN 0019-1035. Retrieved 2 May 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:1506.00762Freely accessible. Bibcode:2015Icar..261...34V. doi:10.1016/j.icarus.2015.08.007. Retrieved 2 May 2017. 
  13. ^ a b "1178 Irmela (1931 EC)". Minor Planet Center. Retrieved 2 May 2017. 
  14. ^ Morrison, D.; Chapman, C. R. (March 1976), "Radiometric diameters for an additional 22 asteroids", Astrophysical Journal, 204, pp. 934–939, Bibcode:2008mgm..conf.2594S, doi:10.1142/9789812834300_0469 

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