WILLIAM & DEBORAH HILLYARD

Solar System -

Jupiter's Moons

Himalia Group

Credit: NASA
Jupiter's moons are grouped as follows.  Select to see details of the moon or the group of moons:


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The Himalia Group of irregular moons comprises the following members: Leda, Himalia, Lysithea, Elara, and S/2000 J 11.  They all orbit Jupiter in a prograde direction at between 11.4 and 13 million kilometers radius, at around 27.5 to the plane of the ecliptic. 
Himalia
Discovered December 3rd, 2904, Himalia is believed to be between about 135 & 170 km across, making it the largest of Jupiter's irregular satellites.  In November 2000, Cassini approached to within 4.4 million km, and it appears that Himalia is elongated and about 150 20 km by 120 20 km.  It is also the heaviest after the four Galilean moons.  Himalia's orbit is eccentric varying between 9,782,900 and 13,082,000 km.  It takes 250.56 days to orbit Jupiter, and about 10 hours to rotate once on its axis.  To the right is a faint image of Himalia taken by New Horizons in 2007 from a distance of 5.5 million km. 

Lysithea

Lysithea was discovered 1938 at Mount Wilson Observatory.  On average, it is only about 36 km across, and orbits in a somewhat eccentric orbit at an average distance of about 11,720,000 km once every 259.2 days. 
Elara
Elara was discovered in 1905 at the Lick Observatory.  On average, it is about 86 km across, and orbits in an eccentric orbit at an average distance of about 11,740,000 km once every 259.64days. 

Dia

Discovered in 2000, Dia (provisionally called S/2000 J 11) is about 4 km in diameter, and orbits in an eccentric orbit at an average distance of 12,555,000 km once every 287 days.  After that, it seemed to disappear, and was believed to have collided with Himalia.  In March 2010, NASA reported that a very faint new ring had been spotted by the New Horizons probe that may be the result of this collision.  The ring had not been seen prior to 2003.  Observations later in 2010 and in 2011 confirmed that the moon was still in orbit. 
Leda
Leda was discovered on September 14, 1974 at the Mount Palomar Observatory.  On average, it is only about 16 km across, and orbits in an eccentric orbit at an average distance of about 11,160,000 km once every 240.92 days.