Elara (moon)

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Elara
Elara2-LB1-mag17.jpg
Elara near the glare of bright Jupiter
Discovery
Discovered byC. D. Perrine
Discovery dateJanuary 5, 1905[1][2]
Orbital characteristics
Mean orbit radius
11,740,000 km (0.07810 AU)[3]
Eccentricity0.22[3]
259.64 d (0.708 a)[3]
3.27 km/s[3]
Inclination26.63° (to the ecliptic)
30.66° (to Jupiter's equator)[3]
Satellite ofJupiter
Physical characteristics
Mean radius
43 km[4]
~23,200 km2
Volume~333,000 km3
Mass8.7×1017 kg
Mean density
2.6 g/cm3 (assumed)[4]
~0.031 m/s2 (0.003 g)
~0.052 km/s
~0.5 d (12 h)
Albedo0.04 (assumed)[4]
Temperature~124 K
16.3[4]

Elara (/ˈɛlərə/ EL-ər-ə; Greek: Ελάρα) is a prograde irregular satellite of Jupiter. It was discovered by Charles Dillon Perrine at Lick Observatory in 1905.[1][2] It is the eighth-largest moon of Jupiter and is named after Elara, one of Zeus's lovers and the mother of the giant Tityos.[5]

Elara did not receive its present name until 1975; before then, it was simply known as Jupiter VII. It was sometimes called "Hera"[6] between 1955 and 1975. It has a mean radius of just 43 kilometres (27 mi), thus it is 2% of the size of Europa. However, it is half the size of Himalia, so it is the second-biggest moon in the Himalia group. It might be a captured type C or D asteroid, for it reflects very little light.

Elara belongs to the Himalia group, five moons orbiting between 11 and 13 gigametres from Jupiter at an inclination of about 27.5°.[3] Its orbital elements are as of January 2000. They are continuously changing due to solar and planetary perturbations.

New Horizons encounter[edit]

In February and March 2007, the New Horizons spacecraft to Pluto captured Elara in several LORRI images from a distance of five million miles.[7]

See also[edit]

References[edit]

  1. ^ a b Perrine, C. D. (1905-02-27). "Satellites of Jupiter". Harvard College Observatory Bulletin. 178.
  2. ^ a b Perrine, C. D. (1905). "The Seventh Satellite of Jupiter". Publications of the Astronomical Society of the Pacific. 17 (101): 62–63. Bibcode:1905PASP...17...56.. doi:10.1086/121624. JSTOR 40691209.
  3. ^ a b c d e f 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.
  4. ^ a b c d "Planetary Satellite Physical Parameters". JPL (Solar System Dynamics). Retrieved 2009-08-10.
  5. ^ Marsden, Brian G. (October 7, 1975). "Satellites of Jupiter". International Astronomical Union. Archived from the original on February 22, 2014.
  6. ^ Payne-Gaposchkin, Cecilia; Katherine Haramundanis (1970). Introduction to Astronomy. Englewood Cliffs, N.J.: Prentice-Hall. ISBN 0-13-478107-4.
  7. ^ Hamilton, Thomas Wm. (2013). Moons of the solar system. Strategic Book Publishing. p. 21. ISBN 1625161751.

External links[edit]