Elara (moon)
From Wikipedia, the free encyclopedia
|
Discovery
|
|
|---|---|
| Discovered by | C. D. Perrine |
| Discovery date | January 2, 1905[1][2] |
| 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 |
| Surface area | ~23,200 km2 |
| Volume | ~333,000 km3 |
| Mass | 8.7×1017 kg |
| Mean density | 2.6 g/cm3 (assumed) |
| 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) |
| Temperature | ~124 K |
Elara (el'-ər-ə, IPA: /ˈɛlərə/; Greek Ελάρα) is a prograde irregular satellite of Jupiter. It was discovered by Charles Dillon Perrine at Lick Observatory in 1905[1][2] and is named after the mother by Zeus of the giant Tityus.[4]
Elara did not receive its present name until 1975; before then, it was simply known as Jupiter VII. It was sometimes called "Hera"[5] 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.
Contents |
[edit] New Horizons encounter
In February and March 2007, the New Horizons spacecraft to Pluto made a number of images of Elara, culminating in photos from a distance of five million miles.
[edit] See also
[edit] References
- ^ a b Perrine, C. D. (1905 February 27). "Satellites of Jupiter". Harvard College Observatory Bulletin 178.
- ^ a b Perrine, C. D. (1905). "The Seventh Satellite of Jupiter". Publications of the Astronomical Society of the Pacific 17 (101): 62–63.
- ^ a b c d e f Jacobson, R. A. (2000). "The orbits of outer Jovian satellites". Astronomical Journal 120: 2679-2686. doi:.
- ^ Marsden, B. G. (7 October 1974). "Satellites of Jupiter". IAUC Circular 2846.
- ^ Payne-Gaposchkin, Cecilia; Katherine Haramundanis (1970). Introduction to Astronomy. Englewood Cliffs, N.J.: Prentice-Hall. ISBN 0-134-78107-4.
[edit] External links
|
||||||||||||||||||||||||||||||||||||||||
