Himalia (moon)

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Himalia
Himalia.png
Himalia as seen by Cassini-Huygens
Discovery
Discovered by C. D. Perrine
Discovery time December 3, 1904
Orbit
Shortest distance from what it orbits around 9,782,900 km
Longest distance from what it orbits around 13,082,000 km
Avgdistance from the center of its orbital path 11,460,000 km[1]
How egg-shaped its orbit is
("eccentricity")
0.16[1]
How long it takes to complete an orbit 250.56 d (0.704 a)[1]
Average speed 3.312 km/s
Angle above the reference plane
("inclination")
27.50° (to the ecliptic)
29.59° (to Jupiter's equator)[1]
What it orbits Jupiter
Size and Other Qualities
Average distance from its center to its surface 85 km
Area of its surface ~90,800 km²
Volume inside it ~2,570,000 km³
Mass 6.7×1018 kg
Average density 2.6 g/cm³ (assumed)
Gravity at its surface ~0.062 m/s2 (0.006 g)
Slowest speed able to escape into space
("escape velocity")
~0.100 km/s
How long it takes to turn around one time
(in relation to the stars)
7.782 h[2]
How much light it reflects 0.04[3]
Avg. surface temp. ~124 K

Himalia is the biggest non-spherical moon of Jupiter. It was found by Charles Dillon Perrine at the Lick Observatory on December 3 1904[4] and is named after the nymph Himalia who bore three sons of Zeus (the Greek equivalent of Jupiter).

Name[change | change source]

Himalia did not get its present name until 1975;[5] before then, it was simply known as Jupiter VI or Jupiter Satellite VI, although calls for a full name appeared shortly after its and Elara's discovery; A.C.D. Crommelin wrote in 1905,

Unfortunately the numeration of Jupiter's satellites is now in precisely the same confusion as that of Saturn's system was before the numbers were abandoned and names substituted. A similar course would seem to be advisable here; the designation V for the inner satellite was tolerated for a time, as it was considered to be in a class by itself; but it has now got companions, so that this subterfuge disappears. The substitution of names for numerals is certainly more poetic.[6]

The moon was sometimes called Hestia,[7] after the Greek goddess, from 1955 to 1975.

Orbit[change | change source]

It is the biggest member of the group that bears its name, the moons orbiting between 11.4 and 13 million kilometers from Jupiter at an inclination of about 27.5°.[8] The orbital elements are as of January 2000.[1] They are changing a lot due to Solar and planetary perturbations.

Physical characteristics[change | change source]

A day on Himalia is only about 7 3/4 hours long.[2] Himalia appears grey, like the other members of its group, similar to a C-type asteroid.[9] Measurements by Cassini confirm a featureless spectrum, with a slight absorption at 3 μm which could indicate the presence of water.[10]

Exploration[change | change source]

In November 2000, the Cassini spacecraft, going to Saturn, made a number of pictures of Himalia, including photos from a distance as close as 4.4 million km. The moon covers only a few pixels, but seems to be a stretched object with axes 150 ± 20 and 120 ± 20 km, close to the Earth-based estimations.[3]

In February and March 2007, the New Horizons spacecraft to Pluto made a series of pictures of Himalia, culminating in photos from a distance of eight million km. Again, Himalia appears only a few pixels across.

References[change | change source]

  1. 1.0 1.1 1.2 1.3 1.4 Jacobson, R. A. (2000). "The orbits of outer Jovian satellites". Astronomical Journal 120: 2679-2686. doi:10.1086/316817.
  2. 2.0 2.1 Pilcher, Frederick; Mottola, Stefano; Denk, Tilmann (2012). "Photometric lightcurve and rotation period of Himalia (Jupiter VI)". Icarus 219 (2): 741-742. doi:10.1016/j.icarus.2012.03.021.
  3. 3.0 3.1 Porco, Carolyn C.; et al. (March 2003). "Cassini Imaging of Jupiter's Atmosphere, Satellites, and Rings". Science 299: 1541-1547. doi:10.1126/science.1079462.
  4. "Discovery of a Sixth Satellite of Jupiter". Astronomical Journal 24 (18): 154B;. January 9, 1905. http://adsabs.harvard.edu//full/seri/AJ.../0024//0000154I002.html.; "Sixth Satellite of Jupiter Confirmed (Himalaia)". Harvard College Observatory Bulletin 175: 1. January 25, 1905. http://adsabs.harvard.edu//full/seri/BHarO/0175//0000001.000.html.; Perrine, C. D. (1905). "Discovery of a Sixth Satellite to Jupiter". Publications of the Astronomical Society of the Pacific 17: 22–23. http://adsabs.harvard.edu//full/seri/PASP./0017//0000022.000.html.; Perrine, C. D. (1905). "Orbits of the sixth and seventh satellites of Jupiter". Astronomische Nachrichten 169: 43–44. http://adsabs.harvard.edu//full/seri/AN.../0169//0000027.000.html.
  5. Marsden, B. G. (7 October 1974). "Satellites of Jupiter". IAUC Circular 2846. http://cfa-www.harvard.edu/iauc/02800/02846.html.
  6. Crommelin, A. C. D. (March 10 1905)). "Provisional Elements of Jupiter's Satellite VI". Monthly Notices of the Royal Astronomical Society 65 (5): 524–527. http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1905MNRAS..65..524C.
  7. Payne-Gaposchkin, Cecilia; Katherine Haramundanis (1970). Introduction to Astronomy. Englewood Cliffs, N.J.: Prentice-Hall. ISBN 0-134-78107-4.
  8. Sheppard, S. S., Jewitt, D. C., Porco, C.; Jupiter's Outer Satellites and Trojans, in Jupiter: The Planet, Satellites and Magnetosphere, edited by Fran Bagenal, Timothy E. Dowling, William B. McKinnon, Cambridge Planetary Science, Vol. 1, Cambridge, UK: Cambridge University Press, ISBN 0-521-81808-7, 2004, pp. 263-280
  9. Rettig, Terrence W. (2001). "Implied Evolutionary Differences of the Jovian Irregular Satellites from a BVR Color Survey". Icarus 154: 313-320. doi:10.1006/icar.2001.6715.
  10. Chamberlain, Matthew A.; Brown, Robert H. (2004). "Near-infrared spectroscopy of Himalia". Icarus 172: 163-169. doi:10.1016/j.icarus.2003.12.016.

Other websites[change | change source]