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|Discovered by||S. B. Nicholson|
|Discovery date||September 28, 1951|
Mean orbit radius
|610.45 d (1.680 a)|
Average orbital speed
148.89° (to the ecliptic)|
149.9° (to Jupiter's equator)
|2.6 g/cm3 (assumed)|
|0.010 m/s2 (0.001 g)|
Ananke (// ə-NANG-kee; Greek: Ανάγκη) is a retrograde irregular moon of Jupiter. It was discovered by Seth Barnes Nicholson at Mount Wilson Observatory in 1951 and is named after the 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 until 1975; before then, it was simply known as Jupiter XII. It was sometimes called "Adrastea" between 1955 and 1975 (Adrastea is now the name of another satellite of Jupiter).
Ananke orbits Jupiter on a high-eccentricity and high-inclination retrograde orbit. Eight irregular satellites orbiting Jupiter have been discovered since 2000 following similar orbits. The orbital elements are as of January 2000. 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.