Himalia (moon)
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Himalia as seen by Cassini-Huygens
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Discovery
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| Discovered by | C. D. Perrine |
| Discovery date | December 3, 1904 |
| Periapsis | 9,782,900 km |
| Apoapsis | 13,082,000 km |
| Mean orbit radius | 11,460,000 km[1] |
| Eccentricity | 0.16[1] |
| Orbital period | 250.56 d (0.704 a)[1] |
| Average orbital speed | 3.312 km/s |
| Inclination | 27.50° (to the ecliptic) 29.59° (to Jupiter's equator)[1] |
| Satellite of | Jupiter |
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Physical characteristics
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| Mean radius | 85 km |
| Surface area | ~90,800 km² |
| Volume | ~2,570,000 km³ |
| Mass | 6.7×1018 kg |
| Mean density | 2.6 g/cm³ (assumed) |
| Equatorial surface gravity | ~0.062 m/s2 (0.006 g) |
| Escape velocity | ~0.100 km/s |
| Sidereal rotation period |
~0.4 d (10 h) |
| Albedo | 0.04[2] |
| Temperature | ~124 K |
Himalia (pronounced /haɪˈmeɪliə/ or /hɪˈmɑliə/, as Greek ‘Ιμαλíα) is the largest irregular satellite of Jupiter. It was discovered by Charles Dillon Perrine at the Lick Observatory on 1904 December 3[3] and is named after the nymph Himalia who bore three sons of Zeus (the Greek equivalent of Jupiter).
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[edit] Name
Himalia did not receive its present name until 1975;[4] 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.[5]
The moon was sometimes called Hestia,[6] after the Greek goddess, from 1955 to 1975.
[edit] Orbit
It is the largest 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°.[7] The orbital elements are as of January 2000.[1] They are continuously changing due to Solar and planetary perturbations.
[edit] Physical characteristics
Himalia appears neutral (grey), like the other members of its group, with colour indices B-V=0.62, V-R= 0.4, similar to a C-type asteroid.[8] Measurements by Cassini confirm a featureless spectrum, with a slight absorption at 3 μm which could indicate the presence of water.[9]
[edit] Exploration
In November 2000, the Cassini spacecraft, enroute to Saturn, made a number of images 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 an elongated object with axes 150 ± 20 and 120 ± 20 km, close to the Earth-based estimations.[2]
In February and March 2007, the New Horizons spacecraft to Pluto made a series of images of Himalia, culminating in photos from a distance of eight million km. Again, Himalia appears only a few pixels across.
[edit] See also
[edit] References
- ^ a b c d e Jacobson, R. A. (2000). "The orbits of outer Jovian satellites". Astronomical Journal 120: 2679-2686. doi:.
- ^ a b Porco, Carolyn C.; et al. (March 2003). "Cassini Imaging of Jupiter's Atmosphere, Satellites, and Rings". Science 299: 1541-1547. doi:.
- ^ "Discovery of a Sixth Satellite of Jupiter" (1905 January 9). Astronomical Journal 24 (18): 154B;.; "Sixth Satellite of Jupiter Confirmed (Himalaia)" (1905 January 25). Harvard College Observatory Bulletin 175: 1.; Perrine, C. D. (1905). "Discovery of a Sixth Satellite to Jupiter". Publications of the Astronomical Society of the Pacific 17: 22–23.; Perrine, C. D. (1905). "Orbits of the sixth and seventh satellites of Jupiter". Astronomische Nachrichten 169: 43–44.
- ^ Marsden, B. G. (7 October 1974). "Satellites of Jupiter". IAUC Circular 2846.
- ^ 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.
- ^ Payne-Gaposchkin, Cecilia; Katherine Haramundanis (1970). Introduction to Astronomy. Englewood Cliffs, N.J.: Prentice-Hall. ISBN 0-134-78107-4.
- ^ 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
- ^ Rettig, Terrence W. (2001). "Implied Evolutionary Differences of the Jovian Irregular Satellites from a BVR Color Survey". Icarus 154: 313-320. doi:.
- ^ Chamberlain, Matthew A.; Brown, Robert H. (2004). "Near-infrared spectroscopy of Himalia". Icarus 172: 163-169. doi:.
[edit] External links
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