Elara (moon)
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 Elara near the glare of bright Jupiter | |
| Discovery | |
|---|---|
| Discovered by | C. D. Perrine |
| Discovery date | January 5, 1905[1][2] |
| Orbital characteristics | |
Mean orbit radius | 11,740,000 km (0.07810 AU)[3] |
| Eccentricity | 0.22[3] |
| 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] |
| ~23,200 km2 | |
| Volume | ~333,000 km3 |
| Mass | 8.7×1017 kg |
Mean density | 2.6 g/cm3 (assumed)[4] |
| ~0.031 m/s2 (0.003 g) | |
| ~0.052 km/s | |
Sidereal rotation period | ~0.5 d (12 h) |
| Albedo | 0.04 (assumed)[4] |
| Temperature | ~124 K |
| 16.3[4] | |
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 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
- ↑ 1.0 1.1 Perrine, C. D.. Satellites of Jupiter. Harvard College Observatory Bulletin 178 (1905-02-27).
- ↑ 2.0 2.1 Perrine, C. D.. The Seventh Satellite of Jupiter. Publications of the Astronomical Society of the Pacific 17 (101) (1905). p. 62–63. doi:10.1086/121624.
- ↑ 3.0 3.1 3.2 3.3 3.4 3.5 Jacobson, R. A.. The orbits of outer Jovian satellites. Astronomical Journal 120 (5) (2000). p. 2679–2686. doi:10.1086/316817.
- ↑ 4.0 4.1 4.2 4.3 Planetary Satellite Physical ParametersJPL (Solar System Dynamics). Retrieved 2009-08-10.
- ↑ Marsden, B. G.. Satellites of Jupiter. IAUC Circular 2846 (7 October 1974).
- ↑ Payne-Gaposchkin, Cecilia. Introduction to Astronomy (1970). Englewood Cliffs, N.J.: Prentice-Hall. ISBN 0-134-78107-4.