Elara

Elara

Elara near the glare of bright Jupiter
Discovery
Discovered by	C. D. Perrine
Discovery date	January 2, 1905[1][2]
Orbital characteristics
Mean orbit radius	11,740,000 km (0.07810 AU)[3]
Eccentricity	0.22[3]
Orbital period	259.64 d (0.708 a)[3]
Average orbital speed	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]
Surface area	~23,200 km2
Volume	~333,000 km3
Mass	8.7 × 1017 kg
Mean density	2.6 g/cm3 (assumed)[4]
Equatorial surface gravity	~0.031 m/s2 (0.003 g)
Escape velocity	~0.052 km/s
Sidereal rotation period	~0.5 d (12 h)
Albedo	0.04 (assumed)[4]
Temperature	~124 K
Apparent magnitude	16.3[4]

Elara (pronounced /ˈɛlərə/ EL-ər-ə, or as in 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 the mother by Zeus of the giant Tityus. I^[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.

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.

See also

• Jupiter's moons in fiction

References

External links

• Elara on 1998-08-15 03:21 UTC (Crédit : OHP/IMCCE/CNRS) / SkyView 23 47 09 -02 40 46
• HORIZONS Web-Interface
• Elara Profile by NASA's Solar System Exploration
• David Jewitt pages
• Jupiter's Known Satellites (by Scott S. Sheppard)