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Elara (moon)

Elara
Elara2-LB1-mag17.jpg
Long-exposure photograph of Elara near Jupiter's bright glare
Discovery [1][2]
Discovered byCharles D. Perrine
Discovery siteLick Observatory
Discovery date5 January 1905
Designations
Designation
Jupiter VII
Pronunciation/ˈɛlərə/[4]
Named after
Ελάρα Elăra[3]
AdjectivesElarian /ɛˈlɛəriən/
Orbital characteristics[5]
Epoch 27 April 2019 (JD 2458600.5)
Observation arc113.70 yr (41,528 days)
0.0782306 AU (11,703,130 km)
Eccentricity0.1961487
+258.65 d
10.93078°
1° 23m 30.67s / day
Inclination30.51712° (to ecliptic)
90.86474°
191.19922°
Satellite ofJupiter
GroupHimalia group
Physical characteristics
Mean diameter
79.9±1.7 km[6]
Albedo0.046±0.007[6]
16.6[7]
9.6[5]

Elara /ˈɛlərə/ is a prograde irregular satellite of Jupiter. It was discovered by Charles Dillon Perrine at Lick Observatory in 1905.[1][8] 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.[9]

Elara did not receive its present name until 1975; before then, it was simply known as Jupiter VII. It was sometimes called "Hera"[10] 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°.[11] Its orbital elements are as of January 2000. They are continuously changing due to solar and planetary perturbations.

New Horizons encounter

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.[12]

See also

References

  1. ^ a b Perrine, C. D. (27 February 1905). "Satellites of Jupiter". Harvard College Observatory Bulletin. 178.
  2. ^ 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. ^ a b "M.P.C. 115889" (PDF). Minor Planet Circular. Minor Planet Center. 27 August 2019.
  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. ^ Sheppard, Scott. "Scott S. Sheppard - Jupiter Moons". Department of Terrestrial Magnetism. Carnegie Institution for Science. Retrieved 26 November 2020.
  8. ^ 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.
  9. ^ Marsden, Brian G. (7 October 1975). "Satellites of Jupiter". International Astronomical Union. Archived from the original on 22 February 2014.
  10. ^ Payne-Gaposchkin, Cecilia; Katherine Haramundanis (1970). Introduction to Astronomy. Englewood Cliffs, N.J.: Prentice-Hall. ISBN 0-13-478107-4.
  11. ^ 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.
  12. ^ Hamilton, Thomas Wm. (2013). Moons of the solar system. Strategic Book Publishing. p. 21. ISBN 978-1625161758.

External links

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