Elara (moon)

Elara is a non-spherical moon of Jupiter. It was found by Charles Dillon Perrine at Lick Observatory in 1905[1][2] and is named after the mother by Zeus of the giant Tityus.[5]

Elara
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 did not get its present name until 1975; before then, it was simply known as Jupiter VII. It was sometimes called "Hera"[6] between 1955 and 1975.

    Elara belongs to the Himalia group, five moons orbiting between 11,000,000 and 13,000,000 km from Jupiter at an inclination of about 27.5°.[3] Its orbital elements are as of January 2000. They are changing a lot due to Solar and planetary perturbations.

    New Horizons encounter

    In February and March 2007, the New Horizons spacecraft to Pluto made a number of pictures of Elara, culminating in photos from a distance of five million miles.

    References
    1. Perrine, C. D. (1905-02-27). "Satellites of Jupiter". Harvard College Observatory Bulletin. 178.
    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.. doi:10.1086/121624. JSTOR 40691209. S2CID 250794880.
    3. 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. S2CID 120372170.
    4. "Planetary Satellite Physical Parameters". JPL (Solar System Dynamics). Retrieved 2009-08-10.
    5. Marsden, B. G. (7 October 1974). "Satellites of Jupiter". IAUC Circular. 2846.
    6. Payne-Gaposchkin, Cecilia; Katherine Haramundanis (1970). Introduction to Astronomy. Englewood Cliffs, N.J.: Prentice-Hall. ISBN 0-134-78107-4.

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