Elara (moon)

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Elara near the glare of bright Jupiter
Discovered byC. D. Perrine
Discovery dateJanuary 5, 1905[1][2]
Jupiter VII
Named after
Ελάρα Elăra[3]
AdjectivesElarian /ɛˈlɛəriən/
Orbital characteristics[5]
11741000 km
+259.6 days
Satellite ofJupiter
GroupHimalia group
Physical characteristics
Mean diameter
79.9±1.7 km[6]
Mass8.7×1017 kg[citation needed]
Mean density
2.6 g/cm3 (assumed)[7]
Temperature~124 K

Elara /ˈɛlərə/ 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 Elara, one of Zeus's lovers and the mother of the giant Tityos.[8]

Elara did not receive its present name until 1975; before then, it was simply known as Jupiter VII. It was sometimes called "Hera"[9] 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 observed by the Wide-field Infrared Survey Explorer (WISE) spacecraft in 2014

Elara belongs to the Himalia group, five moons orbiting between 11 and 13 gigametres from Jupiter at an inclination of about 27.5°.[10] Its orbital elements are as of January 2000. They are continuously changing due to solar and planetary perturbations.

New Horizons encounter[edit]

Elara imaged by the LORRI instrument aboard New Horizons

In February and March 2007, the New Horizons spacecraft to Pluto captured Elara in several LORRI images from a distance of five million miles.[11]

See also[edit]


  1. ^ a b Perrine, C. D. (February 27, 1905). "Satellites of Jupiter". Harvard College Observatory Bulletin. 178.
  2. ^ a b Perrine, C. D. (1905). "The Seventh Satellite of Jupiter". Publications of the Astronomical Society of the Pacific. 17 (101): 62–63. Bibcode:1905PASP...17...56.. doi:10.1086/121624. JSTOR 40691209.
  3. ^ DGE en línea
  4. ^ James Knowles (1851) A Critical Pronouncing Dictionary of the English Language
  5. ^ S.S. Sheppard (2019), Moons of Jupiter, Carnegie Science, on line
  6. ^ a b Grav, T.; Bauer, J. M.; Mainzer, A. K.; Masiero, J. R.; Nugent, C. R.; Cutri, R. M.; et al. (August 2015). "NEOWISE: Observations of the Irregular Satellites of Jupiter and Saturn". The Astrophysical Journal. 809 (1): 9. arXiv:1505.07820. Bibcode:2015ApJ...809....3G. doi:10.1088/0004-637X/809/1/3. S2CID 5834661. 3.
  7. ^ "Planetary Satellite Physical Parameters". JPL (Solar System Dynamics). Retrieved August 10, 2009.
  8. ^ Marsden, Brian G. (October 7, 1975). "Satellites of Jupiter". International Astronomical Union. Archived from the original on February 22, 2014.
  9. ^ Payne-Gaposchkin, Cecilia; Katherine Haramundanis (1970). Introduction to Astronomy. Englewood Cliffs, N.J.: Prentice-Hall. ISBN 0-13-478107-4.
  10. ^ Jacobson, R. A. (2000). "The orbits of outer Jovian satellites" (PDF). Astronomical Journal. 120 (5): 2679–2686. Bibcode:2000AJ....120.2679J. doi:10.1086/316817.
  11. ^ Hamilton, Thomas Wm. (2013). Moons of the solar system. Strategic Book Publishing. p. 21. ISBN 978-1625161758.

External links[edit]