65 Cybele is one of the

largest asteroids The following is a collection of lists of asteroids of the Solar System that are exceptional in some way, such as their size or orbit. For the purposes of this article, "asteroid" refers to minor planets out to the orbit of Neptune, and includes ...

in the

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...

. It is located in the outer

asteroid belt The asteroid belt is a torus-shaped region in the Solar System, centered on the Sun and roughly spanning the space between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies called asteroids ...

. It is thought to be a remnant primordial body. It gives its name to the Cybele group of asteroids that orbit outward from the Sun from the 2:1

orbital resonance In celestial mechanics, orbital resonance occurs when orbiting bodies exert regular, periodic gravitational influence on each other, usually because their orbital periods are related by a ratio of small integers. Most commonly, this relation ...

with

Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...

. The

X-type asteroid The X-group of asteroids collects together several types with similar spectra, but probably quite different compositions. Tholen classification In the Tholen classification, the X-group consists of the following types: * E-type – with high ...

has a relatively short

rotation period In astronomy, the rotation period or spin period of a celestial object (e.g., star, planet, moon, asteroid) has two definitions. The first one corresponds to the '' sidereal rotation period'' (or ''sidereal day''), i.e., the time that the objec ...

of 6.0814 hours. It was discovered by

Wilhelm Tempel Ernst Wilhelm Leberecht Tempel (4 December 1821 – 16 March 1889), normally known as Wilhelm Tempel, was a German astronomer who worked in Marseille until the outbreak of the Franco-Prussian War in 1870, then later moved to Italy. Tempel was b ...

in 1861, and named after

Cybele Cybele ( ; Phrygian: ''Matar Kubileya, Kubeleya'' "Kubeleya Mother", perhaps "Mountain Mother"; Lydian: ''Kuvava''; ''Kybélē'', ''Kybēbē'', ''Kybelis'') is an Anatolian mother goddess; she may have a possible forerunner in the earliest ...

, the earth goddess.

Discovery and naming

''Cybele'' was discovered on 8 March 1861, by German astronomer

from the

Marseilles Observatory Marseille Observatory () is an astronomical observatory located in Marseille, France, with a history that goes back to the early 18th century. In its 1877 incarnation, it was the discovery site of a group of galaxies known as Stephan's Quintet, ...

in southeastern France. A minor controversy arose from its naming process. Tempel had awarded the honour of naming the asteroid to

Carl August von Steinheil Carl August von Steinheil (12 October 1801 – 14 September 1870) was a German physicist, inventor, engineer and astronomer. Biography Steinheil was born in Ribeauvillé, Alsace. He studied law in Erlangen since 1821. He then studied astronomy ...

in recognition of his achievements in

telescope A telescope is a device used to observe distant objects by their emission, Absorption (electromagnetic radiation), absorption, or Reflection (physics), reflection of electromagnetic radiation. Originally, it was an optical instrument using len ...

production. Von Steinheil elected to name it "Maximiliana" after the reigning monarch

Maximilian II of Bavaria Maximilian II (28 November 1811 – 10 March 1864) reigned as King of Bavaria between 1848 and 1864. Unlike his father, King Ludwig I, "King Max" was very popular and took a greater interest in the business of Government than in personal ext ...

. At the time, asteroids were conventionally given classical names, and a number of astronomers protested this contemporary appellation. The name

was chosen instead, referring to the

Phrygia In classical antiquity, Phrygia ( ; , ''Phrygía'') was a kingdom in the west-central part of Anatolia, in what is now Asian Turkey, centered on the Sangarios River. Stories of the heroic age of Greek mythology tell of several legendary Ph ...

n goddess of the earth. (The previously discovered

45 Eugenia 45 Eugenia is a large asteroid of the asteroid belt. It is famed as one of the first asteroids to be found to have a moon orbiting it. It was also the second triple asteroid to be discovered, after 87 Sylvia. Discovery Eugenia was discovered ...

54 Alexandra 54 Alexandra is a carbonaceous asteroid from the intermediate asteroid belt, approximately 155 kilometers in diameter. It was discovered by German-French astronomer Hermann Goldschmidt on 10 September 1858, and named after the German explorer A ...

, and

64 Angelina 64 Angelina is an asteroid from the central region of the asteroid belt, approximately 50 kilometers in diameter. It is an unusually bright form of E-type asteroid. Discovery and naming Angelina was discovered on March 4, 1861, by a prolific ...

had nevertheless also been given non-classical names; 64 Angelina had also been discovered by Tempel, but its name stood despite similar protests.)

Physical characteristics

The first Cybelian stellar

occultation An occultation is an event that occurs when one object is hidden from the observer by another object that passes between them. The term is often used in astronomy, but can also refer to any situation in which an object in the foreground blocks f ...

was observed on 17 October 1979, in the

Soviet Union The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...

. The asteroid appeared to have an irregular shape, with the longest chord being measured as 245 km, closely matching results determined by the IRAS satellite in 1983 ''(see below)''. During the same 1979 occultation, a hint of a possible 11 km wide

minor-planet moon A minor-planet moon is an astronomical object that orbits a minor planet as its natural satellite. , there are 457 minor planets known or suspected to have moons. Discoveries of minor-planet moons (and binary objects, in general) are important ...

at 917 km distance was detected, but has since never been corroborated. As of 2017, neither the ''Asteroid Lightcurve Data Base'' nor ''Johnstons archive'' consider ''Cybele'' to be a

binary asteroid A binary asteroid is a system of two asteroids orbiting their common barycenter. The binary nature of 243 Ida was discovered when the Galileo spacecraft flew by the asteroid in 1993. Since then numerous binary asteroids and several triple a ...

Diameter estimates

Mean diameter In applied sciences, the equivalent radius (or mean radius) is the radius of a circle or sphere with the same perimeter, area, or volume of a non-circular or non-spherical object. The equivalent diameter (or mean diameter) (D) is twice the equiva ...

estimates for ''Cybele'' range between 218.56 and 300.54 kilometers. According to observations by the Infrared Astronomical Satellite

IRAS The Infrared Astronomical Satellite (Dutch language, Dutch: ''Infrarood Astronomische Satelliet'') (IRAS) was the first space telescope to perform a astronomical survey, survey of the entire night sky at infrared wavelengths. Launched on 25 Janu ...

in 1983, the asteroid has a diameter of 237.26 km. The

NEOWISE Wide-field Infrared Survey Explorer (WISE, observatory code C51, Explorer 92 and MIDEX-6) was a NASA infrared astronomy space telescope in the Explorers Program launched in December 2009.. . WISE discovered thousands of minor planets and nu ...

mission of NASA's

Wide-field Infrared Survey Explorer Wide-field Infrared Survey Explorer (WISE, List of observatory codes, observatory code C51, Explorer 92 and MIDEX-6) was a NASA infrared astronomy Space observatory, space telescope in the Explorers Program launched in December 2009.. . WISE L ...

gave a diameter of 218.56 and 276.58 km. The largest estimates of 300.54 km is from the Japanese Akari satellite. In 2004, Müller estimated ''Cybele'' using thermophysical modelling (TPM) to have dimensions of 302 × 290 × 232 km, which corresponds to a mean-diameter of 273.0 km. Observations in 2021 show that Cybele's present shape very closely matches what would be expected if it were in

hydrostatic equilibrium In fluid mechanics, hydrostatic equilibrium, also called hydrostatic balance and hydrostasy, is the condition of a fluid or plastic solid at rest, which occurs when external forces, such as gravity, are balanced by a pressure-gradient force. I ...

, in contrast to the other large Cybele asteroids

87 Sylvia 87 Sylvia is one of the largest asteroids (approximately tied for 7th place, to within measurement uncertainties). It is the parent body of the Sylvia family and member of Cybele group located beyond the main asteroid belt (see minor-planet ...

and

107 Camilla 107 Camilla is one of the largest asteroids from the outermost edge of the asteroid belt, approximately in diameter. It is a member of the Sylvia family and located within the Cybele group. It was discovered on 17 November 1868, by English as ...

. This suggests a transition point between irregular small asteroids and equilibrium larger bodies at around 1.5 × 10¹⁹ kg, and makes it possible that outer Solar System bodies at least 260 km in diameter might have formed in equilibrium (note Saturn IX Phoebe, which at 212 km diameter probably formed in equilibrium). However, it is not certain if Cybele's current shape is its primordial one, or if it is the result of a large impact as on the very round

10 Hygiea 10 Hygiea is a large asteroid located in the outer main asteroid belt between the orbits of Mars and Jupiter. It was the tenth known asteroid, discovered on 12 April 1849 by Italian astronomer Annibale de Gasparis at the Astronomical Observa ...

and

31 Euphrosyne 31 Euphrosyne is one of the largest asteroids (approximately tied for 7th place, to within measurement uncertainties). It was discovered by James Ferguson on September 1, 1854, the first asteroid found from North America. It is named after Euphr ...

. Today no Cybele family is observable, but since Cybele orbits in a rather unstable region, any such family would be dispersed within 2 billion years. Cybele's larger density compared to Sylvia and Camilla does somewhat favour the first hypothesis, though. (Sylvia and Camilla experienced impacts, as evidenced by their satellites and by the

Sylvia family An asteroid family is a population of asteroids that share similar proper orbital elements, such as semimajor axis, eccentricity (orbit), eccentricity, and orbital inclination. The members of the families are thought to be Collisional family, fra ...

Spectrum

Examination of the asteroid's infrared spectrum shows an absorption feature that is similar to the one present in the spectrum of

24 Themis 24 Themis is one of the largest asteroids in the asteroid belt. At roughly in diameter, it is also the largest member of the Themistian family. It was discovered by Annibale de Gasparis on 5 April 1853. It is named after Themis, the personif ...

. 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.

Recent occultations

On August 24, 2008, Cybele

occulted An occultation is an event that occurs when one object is hidden from the observer by another object that passes between them. The term is often used in astronomy, but can also refer to any situation in which an object in the foreground blocks f ...

2UCAC 24389317, a 12.7-

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

star in the constellation

Ophiuchus Ophiuchus () is a large constellation straddling the celestial equator. Its name comes from the Ancient Greek (), meaning "serpent-bearer", and it is commonly represented as a man grasping a snake. The serpent is represented by the constellati ...

which showed a long axis of at least 294 km. On 11 October 2009, Cybele occulted a 13.4-magnitude star in the constellation Aquarius.

Notes

References

External links

Asteroid Lightcurve Database (LCDB)
query form

)
Dictionary of Minor Planet Names
Google books

at Observatoire de Genève, Raoul Behrend

– Minor Planet Center * * {{DEFAULTSORT:Cybele 000065 Discoveries by Wilhelm Tempel Named minor planets 000065 000065 000065 000065 18610308