65 Cybele

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65 Cybele
65 Cybele.png
3D shape model of Cybele from ground-based observations.
Discovered by Ernst Wilhelm Tempel
Discovery date March 8, 1861
Pronunciation /ˈsɪbl/ SIB-əl-ee
Named after
outer main belt[1] (Cybele)
Orbital characteristics[1]
Epoch December 31, 2006 (JD 2454100.5)
Aphelion 567.544 Gm (3.794 AU)
Perihelion 459.654 Gm (3.073 AU)
513.599 Gm (3.433 AU)
Eccentricity 0.105
2323.521 d (6.36 a)
16.03 km/s
Inclination 3.548°
Physical characteristics
Dimensions 302×290×232 km[2]
273.0±11.9 km[2]
237.3 km IRAS[1]
Mass 1.78×1019 kg[3]
Mean density
0.99±0.20 g/cm³[3]
0.0663 m/s²
0.1255 km/s
4.041 h[1]
Albedo 0.050 ± 0.005[2]
Temperature ~150 K
Spectral type
10.67 to 13.64

65 Cybele is one of the largest asteroids in the Solar System and is located in the outer asteroid belt.[4] It gives its name to the Cybele family of asteroids[4] that orbit outward from the Sun from the 2:1 orbital resonance with Jupiter. Cybele is a X-type asteroid, meaning that it is dark in color and carbonaceous[clarification needed] in composition. It was discovered in 1861 by Ernst Tempel and named after Cybele, the earth goddess.

Discovery and naming[edit]

Cybele was discovered on March 8, 1861, by Ernst Tempel from the Marseilles Observatory. A minor controversy arose from its naming process. Tempel had awarded the honour of naming the asteroid to Carl August von Steinheil in recognition of his achievements in telescope production. Von Steinheil elected to name it "Maximiliana" after the reigning monarch Maximilian II of Bavaria. At the time, asteroids were conventionally given classical names, and a number of astronomers protested this contemporary appellation. The name Cybele was chosen instead, referring to the Phrygian goddess of the earth.[5]

Physical characteristics[edit]

The first Cybelian stellar occultation was observed on October 17, 1979 in the Soviet Union. The asteroid appeared to have an irregular shape, with the longest chord being measured as 245 km, closely matching the diameter of 237 km determined by the IRAS satellite in 1983. During the same 1979 occultation, a hint of a possible 11 km wide satellite was detected.[6]

The diameter from IRAS observations in 1983 is 237±4 km.[1] In 1985, Green estimated Cybele to have a diameter of 330 km.[2] In 2004, Müller estimated Cybele using thermophysical modelling (TPM) to have dimensions of 302×290×232 km.[2]

In 2007, David Weintraub suggested that it might be in hydrostatic equilibrium,[7] but it this is no longer considered a possibility.


Examination of the asteroid's infrared spectrum shows an absorption feature that is similar to the one present in the spectrum of 24 Themis. This can be explained by the presence of water ice. The asteroid may be covered in a layer of fine silicate dust mixed with small amounts of water-ice and organic solids.[8]

Recent occultations[edit]

On August 24, 2008, Cybele occulted 2UCAC 24389317, a 12.7-magnitude star in the constellation Ophiuchus which showed a long axis of at least 294 km.[9] On October 11, 2009, Cybele occulted a 13.4-magnitude star in the constellation Aquarius.[10]


  1. ^ a b c d e f g h "JPL Small-Body Database Browser: 65 Cybele". 2010-11-23 last obs. Retrieved 2008-11-25. 
  2. ^ a b c d e Müller, T. G; Blommaert, J. A. D. L. (2004). "65 Cybele in the thermal infrared: Multiple observations and thermophysical analysis". Astronomy and Astrophysics. 418: 347–356. arXiv:astro-ph/0401458Freely accessible. Bibcode:2004A&A...418..347M. doi:10.1051/0004-6361:20040025. 
  3. ^ a b Jim Baer (2008). "Recent Asteroid Mass Determinations". Personal Website. Retrieved 2008-11-28. 
  4. ^ a b Linda T. Elkins-Tanton - Asteroids, Meteorites, and Comets (2010) - Page 96 (Google Books)
  5. ^ Lutz D. Schmadel, Dictionary of Minor Planet Names, p.21.
  6. ^ "IAUC 3439: 1979l; Occn OF AGK3 +19 599 BY (65)". MPC (Circular No. 3439). 1980-01-04. Retrieved 2004-06-18. 
  7. ^ Weintraub, David A. (2007). Is Pluto a Planet?. Princeton, New Jersey: Princeton University Press. p. 202. ISBN 978-0-691-12348-6. 
  8. ^ Licandro, J; Campins, H; Kelley, M. S..; Hargrove, K.; Pinilla-Alonso, N.; Cruikshank,D. P.; Rivkin, A. S.; Emery, J. (January 2011). "(65) Cybele: detection of small silicate grains, water-ice, and organics". Astronomy and Astrophysics. 525: A.34. Bibcode:2011A&A...525A..34L. doi:10.1051/0004-6361/201015339. 
  9. ^ IOTA. "(65) Cybele 2008 Aug 24 profile". Retrieved 2010-12-02. 
  10. ^ Steve Preston. "(65) Cybele / 2UCAC 28838190 event on 2009 Oct 11, 01:30 UT". Retrieved 2009-09-21. 

External links[edit]