Ananke (moon)

Infobox Planet
name = Ananke
bgcolour = #ffc0c0
discovery = yes
discoverer = S. B. Nicholson
discovered = September 28, 1951
mean_orbit_radius = 21,280,000 kmcite journal |last=Jacobson |first=R. A. |authorlink=Robert A. Jacobson |title=The Orbits of Outer Jovian Satellites |journal=Astronomical Journal |year=2000 |volume=120 |pages=2679–2686 |doi=10.1086/316817]
eccentricity = 0.24
periapsis = 12,567,000 km
apoapsis = 29,063,500 km
period = 610.45 d (1.680 a)
avg_speed = 2.367 km/s
inclination = 148.89° (to the ecliptic) 149.9° (to Jupiter's equator)
satellite_of = Jupiter
physical_characteristics = yes
mean_radius = 14 km
surface_area = ~2500 km²
volume = ~11,500 km³
mass = 3.0e|16 kg
density = 2.6 g/cm³ (assumed)
surface_grav = 0.010 m/s² (0.001 g)
escape_velocity = ~0.017 km/s
albedo = 0.04 (assumed)
single_temperature = ~124 K

Ananke (pron-en|əˈnæŋki respell|ə|NANG|kee, or as in Greek "Ανάγκη)" is a retrograde irregular satellite of Jupiter. It was discovered by Seth Barnes Nicholson at Mount Wilson Observatory in 1951cite journal|last=Nicholson|first=S. B.| url=http://adsabs.harvard.edu//full/seri/PASP./0063//0000297.000.html|title=An unidentified object near Jupiter, probably a new satellite|journal=Publications of the Astronomical Society of the Pacific|volume=63|issue=375|year=1951|pages=297–299|doi=10.1086/126402] and is named after the mythological Ananke, the mother of Adrastea by Jupiter. The adjectival form of the name is "Anankean" .

Ananke did not receive its present namecite journal|last=Nicholson|first=S.B.|title=S. B. Nicholson declines to name the satellites of Jupiter he has discovered| url=http://adsabs.harvard.edu//full/seri/PASP./0051//0000093.000.html|journal=Publications of the Astronomical Society of the Pacific|volume=51|issue=300|pages=85–94|date=April 1939|doi=10.1086/125010] until 1975;cite journal| last=Marsden|first=B. G.|title=Satellites of Jupiter|journal=IAUC Circular |volume=2846|date=7 October 1974|url=http://cfa-www.harvard.edu/iauc/02800/02846.html] before then, it was simply known as nowrap|Jupiter XII. It was sometimes called "Adrastea"cite book| last=Payne-Gaposchkin|first=Cecilia|coauthors=Katherine Haramundanis|title=Introduction to Astronomy|year=1970|publisher=Prentice-Hall|location=Englewood Cliffs, N.J.|isbn=0-134-78107-4] between 1955 and 1975. Note that 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°.Sheppard, S. S., Jewitt, D. C., Porco, C.; [http://www.ifa.hawaii.edu/~jewitt/papers/JUPITER/JSP.2003.pdf "Jupiter's Outer Satellites and Trojans"] , 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]

Orbit

Ananke orbits Jupiter on a high eccentricity and high inclination retrograde orbit. Eight irregular satellites discovered since 2000 follow 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.

Given these orbital elements and the physical characteristics known so far, Ananke is thought to be the largest remnantcite journal|last=Sheppard|first=S.S.|coauthors=Jewitt, D.C.|title=An abundant population of small irregular satellites around Jupiter|journal=Nature|volume=423|year=2003|pages=261–263 |ura=http://www.ifa.hawaii.edu/~jewitt/papers/JSATS/SJ2003.pdf|doi=10.1038/nature01584] of an original break-up forming the Ananke group.cite journal|last=Nesvorný|first=D.|coauthors=Beaugé, C.;Dones, L.|title=Collisional Origin of Families of Irregular Satellites| journal=The Astronomical Journal|volume=127|year=2004|pages=1768–1783|url=http://www.iop.org/EJ/article/1538-3881/127/3/1768/203442.html|doi=10.1086/382099] cite journal|last=Grav|first=Tommy|coauthers=Holman, M. J.; Gladman, B. J.; Aksnes, K.|title=Photometric survey of the irregular satellites|journal=Icarus|volume=166|year=2003|pages=33–45|doi=10.1016/j.icarus.2003.07.005 ]

Physical characteristics

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

The infrared spectrum is similar to P-type asteroids but with a possible indication of water.cite journal|last=Grav|first=Tommy|coauthers=Holman, Matthew J.|title=Near-Infrared Photometry of the Irregular Satellites of Jupiter and Saturn|journal=The Astrophysical Journal|volume=605|year=2004|pages=L141–L144| url=http://arxiv.org/abs/astro-ph/0312571|doi=10.1086/420881]

ee also

*Irregular satellites

References

#

Ephemeris [http://cfa-www.harvard.edu/iau/NatSats/NaturalSatellites.html IAU-MPC NSES]

External links

* [http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jup_Ananke Ananke Profile] by [http://solarsystem.nasa.gov NASA's Solar System Exploration]
* [http://www.ifa.hawaii.edu/~jewitt/irregulars.html David Jewitt pages]
* [http://www.ifa.hawaii.edu/~sheppard/satellites/jupsatdata.html Scott Sheppard pages]