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Ananke (/əˈnæŋk/ 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[3] 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.

Discovered byS. B. Nicholson
Discovery dateSeptember 28, 1951
Orbital characteristics
Periapsis12,567,000 km
Apoapsis29,063,500 km
Mean orbit radius
21,280,000 km[1]
610.45 d (1.680 a)[1]
2.367 km/s
Inclination148.89° (to the ecliptic)
149.9° (to Jupiter's equator)[1]
Satellite ofJupiter
Physical characteristics
Mean radius
14 km[2]
~2500 km2
Volume~11,500 km3
Mass4.0×1016 kg
Mean density
2.6 g/cm3 (assumed)
0.010 m/s2 (0.001 g)
~0.017 km/s
Albedo0.04 (assumed)[2]
Temperature~124 K

Ananke did not receive its present name[4] until 1975;[5] before then, it was simply known as Jupiter XII. It was sometimes called "Adrastea"[6] 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°.[2]


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.[2] The orbital elements are as of January 2000.[1] 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[7] of an original break-up forming the Ananke group.[8][9]

Physical characteristicsEdit

In the visible spectrum, Ananke appears neutral to light-red (colour indices B-V=0.90 V-R=0.38).[9]

The infrared spectrum is similar to P-type asteroids but with a possible indication of water.[10]

Retrograde irregular satellites of Jupiter.

See alsoEdit


  1. ^ a b c d e Jacobson, R. A. (2000). "The Orbits of Outer Jovian Satellites" (PDF). Astronomical Journal. 120 (5): 2679–2686. Bibcode:2000AJ....120.2679J. doi:10.1086/316817.
  2. ^ a b c d Sheppard, S. S., Jewitt, D. C., Porco, C.; Jupiter's Outer Satellites and Trojans Archived 2007-06-14 at the Wayback Machine, in Jupiter: The Planet, Satellites and Magnetosphere, edited by Fran Bagenal, Timothy E. Dowling, William B. McKinnon, Cambridge Planetary Science, Vol. 1, Cambridge, UK: Cambridge University Press, ISBN 0-521-81808-7, 2004, pp. 263-280
  3. ^ Nicholson, S. B. (1951). "An unidentified object near Jupiter, probably a new satellite". Publications of the Astronomical Society of the Pacific. 63 (375): 297–299. Bibcode:1951PASP...63..297N. doi:10.1086/126402.
  4. ^ Nicholson, S.B. (April 1939). "S. B. Nicholson declines to name the satellites of Jupiter he has discovered". Publications of the Astronomical Society of the Pacific. 51 (300): 85–94. Bibcode:1939PASP...51...85N. doi:10.1086/125010.
  5. ^ Marsden, B. G. (7 October 1974). "Satellites of Jupiter". IAU Circular. 2846.
  6. ^ Payne-Gaposchkin, Cecilia; Katherine Haramundanis (1970). Introduction to Astronomy. Englewood Cliffs, N.J.: Prentice-Hall. ISBN 0-13-478107-4.
  7. ^ Sheppard, S.S.; Jewitt, D.C. (2003). "An abundant population of small irregular satellites around Jupiter" (PDF). Nature. 423 (6937): 261–263. Bibcode:2003Natur.423..261S. doi:10.1038/nature01584. PMID 12748634. Archived from the original (PDF) on August 13, 2006.
  8. ^ Nesvorný, D.; Beaugé, C.; Dones, L. (2004). "Collisional Origin of Families of Irregular Satellites". The Astronomical Journal. 127 (3): 1768–1783. Bibcode:2004AJ....127.1768N. doi:10.1086/382099.
  9. ^ a b Grav, Tommy; Holman, M. J.; Gladman, B. J.; Aksnes, K. (2003). "Photometric survey of the irregular satellites". Icarus. 166 (1): 33–45. arXiv:astro-ph/0301016. Bibcode:2003Icar..166...33G. doi:10.1016/j.icarus.2003.07.005.
  10. ^ Grav, Tommy; Holman, Matthew J. (2004). "Near-Infrared Photometry of the Irregular Satellites of Jupiter and Saturn". The Astrophysical Journal. 605 (2): L141–L144. arXiv:astro-ph/0312571. Bibcode:2004ApJ...605L.141G. doi:10.1086/420881.


External linksEdit