Elara is a prograde irregular satellite of Jupiter and the second biggest satellite in the Himalia group.
Elara is the 8th largest moon of Jupiter and 50th largest moon in the Solar System currently known.
Discovery
Elara was discovered on 5 January 1905 by Charles Dillon Perrine in photographs taken with the Crossley 36-inch reflector at Lick Observatory.
Naming
Elara the moon is named for one of the lovers of Zeus, the Greek equivalent of the Roman god Jupiter.
In Greek mythology, Elara was the daughter of King Orchomenus and mother of Tityos. She was one of Zeus' lovers and he hid her from his wife, Hera, by placing her deep beneath the earth. This was where she gave birth to Tityos, a giant who is sometimes said to be the son of Gaia, the earth goddess, for this reason. It is further added that Elara died in labour because of the enormous size of her baby.
Stats
Diameter (mean): 86 km
Semi-major axis: 11,741,000 km
Orbital Period: 259.64 days
Rotation Period: 12 hours
Orbit
Elara belongs to the Himalia group, a family of Jovian satellites which have similar orbits and appearance, with orbital elements continuously changing due to solar and planetary perturbations.
Formation
Elara may be a chunk of an asteroid (a C or D class asteroid, judging by the fact that it reflects only about 4% of the light it receives), which was broken apart in a collision either before or after being captured by Jupiter's gravity. In this scenario, the other pieces became the other moons in the Himalia group.
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