Elara (moon)
Elara also known as , is the second largest irregular satellite of Jupiter.
Discovery and naming
Elara was discovered by Charles Dillon Perrine of the Lick Observatory on January 6, 1905, the day after the discovery of Himalia, also by Perrine, was announced. Confirmation of the discovery was delayed until the 21st of February due to poor weather conditions.Its 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 . It was sometimes called "Hera" between 1955 and 1975.
Orbit
Elara orbits Jupiter at an average distance of 11,703,130 km km in 258,65 days, at an inclination of about 30° to the ecliptic, in a prograde direction and with an eccentricity of 0.196. Its orbit is continuously changing due to solar and planetary perturbations.Elara belongs to the Himalia group, a prograde group of moons orbiting between 11 and 13 Gm from Jupiter at an inclinations between 27 and 30°, and eccentricities between 0.11 and 0.24.
Physical characteristics
Elara has a diameter of about 80 kilometers, with a measured albedo of about 4.6%, making it the eighth largest moon of Jupiter. It is about 2.6% of the size of Europa. It is half the size of Himalia, making it the second largest member of the Himalia group.Like the other members of the Himalia group, the satellite appears gray, which is typical for C-type asteroids.
A measured low beam value of 0.79 ± 0.03 indicates that Elara has considerable surface roughness.