Elara (moon)

Elara

Elara near the glare of bright Jupiter
Discovery
Discovered by C. D. Perrine
Discovery date January 5, 1905[1][2]
Orbital characteristics
Mean orbit radius
 11,740,000 km (0.07810 AU)[3]
Eccentricity 0.22[3]
259.64 d (0.708 a)[3]
3.27 km/s[3]
Inclination 26.63° (to the ecliptic)
30.66° (to Jupiter's equator)[3]
Satellite of Jupiter
Physical characteristics
Mean radius
 43 km[4]
~23,200 km2
Volume ~333,000 km3
Mass 8.7×1017 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)
Albedo 0.04 (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 km, 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 Gm 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

    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

    References

    1. 1 2 Perrine, C. D. (1905-02-27). "Satellites of Jupiter". Harvard College Observatory Bulletin. 178.
    2. 1 2 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.. JSTOR 40691209. doi:10.1086/121624.
    3. 1 2 3 4 5 6 Jacobson, R. A. (2000). "The orbits of outer Jovian satellites". Astronomical Journal. 120 (5): 2679–2686. Bibcode:2000AJ....120.2679J. doi:10.1086/316817.
    4. 1 2 3 4 "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. Retrieved 8 February 2015.
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