Ananke (moon)
Ananke (moon)
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Ananke (moon)

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Ananke
Ananke photographed by the Haute-Provence Observatory in August 1998
Discovery[1]
Discovered bySeth B. Nicholson
Discovery siteMt. Wilson Observatory
Discovery date28 September 1951
Designations
Designation
Jupiter XII
Pronunciation/əˈnæŋk/[2]
Named after
Ἀνάγκη Anagkē
AdjectivesAnankean /ænəŋˈkən/[3]
Orbital characteristics[4]
Epoch 17 December 2020 (JD 2459200.5)
Observation arc69.05 yr (24,338 days)
0.1406602 AU (21,042,470 km)
Eccentricity0.1747248
–623.59 d
339.61045°
0° 34m 38.281s / day
Inclination148.67482° (to ecliptic)
86.44368°
135.63033°
Satellite ofJupiter
GroupAnanke group
Physical characteristics
29.1±0.6 km[5]
Mass1.68×1016 kg (calculated)
Mean density
1.30 g/cm3 (assumed)[6]
8.31±0.15 h[7]
Albedo0.038±0.006[5]
18.9[8]
11.7[4]

Ananke (/əˈnæŋki/) is a retrograde irregular moon of Jupiter. It was discovered by Seth Barnes Nicholson at Mount Wilson Observatory in 1951.[1] It is named after the Greek mythological Ananke, the personification of necessity, and the mother of the Moirai (Fates) by Zeus. The adjectival form of the name is Anankean.

Ananke did not receive its present name[9] until 1975;[10] before then, it was simply known as Jupiter XII. It was sometimes called "Adrastea"[11] between 1955 and 1975 (Adrastea is now the name of another satellite of Jupiter).

Ananke gives its name to the Ananke group, retrograde irregular moons which orbit Jupiter between 19.3 and 22.7 Gm, at inclinations of roughly 150°.[12]

Orbit

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Retrograde irregular satellites of Jupiter.

Ananke orbits Jupiter on a high-eccentricity and high-inclination retrograde orbit. Fifteen irregular satellites orbiting Jupiter have been discovered since 2000 following similar orbits.[12] The orbital elements are as of January 2000.[13] They are continuously changing due to solar and planetary perturbations. The diagram illustrates Ananke's orbit in relation to other retrograde irregular satellites of Jupiter. The eccentricity of selected orbits is represented by the yellow segments (extending from the pericentre to the apocentre). The outermost regular satellite Callisto is located for reference.

Given these orbital elements and the physical characteristics known so far, Ananke is thought to be the largest remnant[14] of an original break-up, forming the Ananke group.[15][16]

Physical characteristics

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Single-exposure image of Ananke by the Wide-field Infrared Survey Explorer (WISE) spacecraft in 2010

In the visible spectrum, Ananke appears neutral to light-red (colour indices B-V=0.90 V-R=0.38).[16]

The infrared spectrum is similar to P-type asteroids but with a possible indication of water.[17]

See also

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References

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