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Elara near the glare of bright Jupiter
|Discovered by||C. D. Perrine|
|Discovery date||January 5, 1905|
Mean orbit radius
|11,740,000 km (0.07810 AU)|
|259.64 d (0.708 a)|
Average orbital speed
|Inclination||26.63° (to the ecliptic)
30.66° (to Jupiter's equator)
|2.6 g/cm3 (assumed)|
|~0.031 m/s2 (0.003 g)|
Sidereal rotation period
|~0.5 d (12 h)|
Elara (// EL-ər-ə; Greek: Ελάρα) is a prograde irregular satellite of Jupiter. It was discovered by Charles Dillon Perrine at Lick Observatory in 1905. 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.
Elara did not receive its present name until 1975; before then, it was simply known as Jupiter VII. It was sometimes called "Hera" 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°. Its orbital elements are as of January 2000. They are continuously changing due to solar and planetary perturbations.