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Star field showing Cybele towards the lower right.
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Discovery
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| Discovered by | Ernst Wilhelm Tempel |
| Discovery date | March 8, 1861 |
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Designations
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| Named after | Cybele |
| Alternate name(s) | |
| Minor planet category |
outer main belt[1] (Cybele) |
| Epoch December 31, 2006 (JD 2454100.5) | |
| Aphelion | 567.544 Gm (3.794 AU) |
| Perihelion | 459.654 Gm (3.073 AU) |
| Semi-major axis | 513.599 Gm (3.433 AU) |
| Eccentricity | 0.105 |
| Orbital period | 2323.521 d (6.36 a) |
| Average orbital speed | 16.03 km/s |
| Mean anomaly | 279.683° |
| Inclination | 3.548° |
| Longitude of ascending node | 155.808° |
| Argument of perihelion | 105.757° |
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Physical characteristics
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| 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 | 2.55±0.22 g/cm³[3] |
| Equatorial surface gravity | 0.0663 m/s² |
| Escape velocity | 0.1255 km/s |
| Rotation period | 4.041 h[1] |
| Albedo | 0.050 ± 0.005[2] 0.071[1] |
| Temperature | ~150 K |
| Spectral type | C |
| Apparent magnitude | 10.67 to 13.64 |
| Absolute magnitude (H) | 6.62[1] |
65 Cybele ( /ˈsɪbɨliː/ sib-əl-ee; Greek: Κυβέλη) 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 C-type asteroid, meaning that it is dark in color and carbonaceous in composition. It was discovered in 1861 by Ernst Tempel and named after Cybele the earth goddess.
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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]
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]
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] The diameter from IRAS observations in 1983 are listed on the JPL Small-Body Database as 237.26 km (118.63 km radius) as of 2010.[1]
Examination of the asteroid's infrared spectrum shows an absorption feature that is similar to 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.[7]
On August 24, 2008, Cybele occulted 2UCAC 24389317, a 12.7 magnitude star in the constellation Ophiuchus.[8] On October 11, 2009, Cybele occulted a 13.4 magnitude star in the constellation Aquarius.[9]
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