Himalia (moon)

Infobox Planet
name = Himalia


bgcolour = #ffc0c0
caption = Himalia as seen by Cassini-Huygens
discovery = yes
discoverer = C. D. Perrine
discovered = December 16, 1904
mean_orbit_radius = 11,460,000 kmcite journal| last=Jacobson| first=R. A.|title=The orbits of outer Jovian satellites|journal=Astronomical Journal| year=2000| volume=120| pages=2679–2686|doi=10.1086/316817]
eccentricity = 0.16
periapsis = 9,782,900 km
apoapsis = 13,082,000 km
period = 250.56 d (0.704 a)
avg_speed = 3.312 km/s
inclination = 27.50° (to the ecliptic) 29.59° (to Jupiter's equator)
satellite_of = Jupiter
physical_characteristics = yes
mean_radius = 85 km
surface_area = ~90,800 km²
volume = ~2,570,000 km³
mass = 6.7e|18 kg
density = 2.6 g/cm³ (assumed)
surface_grav = ~0.062 m/s² (0.006 g)
escape_velocity = ~0.100 km/s
sidereal_day = ~0.4 d (10 h)
albedo = 0.04cite journal|last=Porco|first=Carolyn C.|coauthors=et al.|title=Cassini Imaging of Jupiter's Atmosphere, Satellites, and Rings|journal=Science|volume=299|month=March | year=2003|pages=1541–1547|doi=10.1126/science.1079462|pmid=12624258]
single_temperature = ~124 K

Himalia (pron-en|haɪˈmeɪliə respell|hye|MAY|lee-ə, or IPAlink-en|hɪˈmɑːliə respell|hi|MAH|lee-ə as in Greek "‘Ιμαλíα)" is the largest irregular satellite of Jupiter. It was discovered by Charles Dillon Perrine at the Lick Observatory on 1904 December 3 [cite journal|title=Discovery of a Sixth Satellite of Jupiter|journal=Astronomical Journal| volume=24|issue=18|date=1905 January 9| pages=154B;|url=http://adsabs.harvard.edu//full/seri/AJ.../0024//0000154I002.html ; cite journal|title=Sixth Satellite of Jupiter Confirmed (Himalaia)|url=http://adsabs.harvard.edu//full/seri/BHarO/0175//0000001.000.html|journal= Harvard College Observatory Bulletin|volume=175|date=1905 January 25|pages=1; cite journal|last=Perrine|first=C. D.| url=http://adsabs.harvard.edu//full/seri/PASP./0017//0000022.000.html|title=Discovery of a Sixth Satellite to Jupiter|journal=Publications of the Astronomical Society of the Pacific|volume=17|year=1905|pages=22–23|doi=10.1086/121619; cite journal|last=Perrine|first=C. D.| url=http://adsabs.harvard.edu//full/seri/AN.../0169//0000027.000.html|title=Orbits of the sixth and seventh satellites of Jupiter|journal=Astronomische Nachrichten|volume=169|year=1905|pages=43–44|doi=10.1002/asna.19051690304] and is named after the nymph Himalia who bore three sons of Zeus (the Greek equivalent of Jupiter).

Name

Himalia did not receive its present name until 1975;cite journal| last=Marsden|first=B. G.|title=Satellites of Jupiter|journal=IAUC Circular |volume=2846|date=7 October 1974|url=http://cfa-www.harvard.edu/iauc/02800/02846.html] before then, it was simply known as nowrap|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.cite journal|last=Crommelin|first=A. C. D.| url=http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1905MNRAS..65..524C|title=Provisional Elements of Jupiter's Satellite VI|journal=Monthly Notices of the Royal Astronomical Society|volume=65|issue=5|pages=524–527|date=March 10 1905)]

The moon was sometimes called Hestia,cite book| last=Payne-Gaposchkin|first=Cecilia|coauthors=Katherine Haramundanis|title=Introduction to Astronomy|year=1970|publisher=Prentice-Hall|location=Englewood Cliffs, N.J.|isbn=0-134-78107-4] after the Greek goddess, from 1955 to 1975.

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°.Sheppard, S. S., Jewitt, D. C., Porco, C.; [http://www.ifa.hawaii.edu/~jewitt/papers/JUPITER/JSP.2003.pdf "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] The orbital elements are as of January 2000. They are continuously changing due to Solar and planetary perturbations.

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.cite journal|last=Rettig|first=Terrence W.|coauthers=Walsh, Kevin; and Consolmagno, Guy|title=Implied Evolutionary Differences of the Jovian Irregular Satellites from a BVR Color Survey|journal=Icarus| volume=154|year=2001|pages=313–320|doi=10.1006/icar.2001.6715] Measurements by "Cassini" confirm a featureless spectrum, with a slight absorption at 3 μm which could indicate the presence of water.cite journal|last=Chamberlain|first=Matthew A.|coauthors=Brown, Robert H.| title=Near-infrared spectroscopy of Himalia|journal=Icarus|volume=172|year=2004|pages=163–169|doi=10.1016/j.icarus.2003.12.016]

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.

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.

ee also

*Irregular satellites

References

External links

* [http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jup_Himalia Himalia Profile] by [http://solarsystem.nasa.gov NASA's Solar System Exploration]
* [http://www.ifa.hawaii.edu/~jewitt/irregulars.html David Jewitt pages]
* [http://www.ifa.hawaii.edu/~sheppard/satellites/jupsatdata.html Scott Sheppard pages]