5th Largest Moon of Jupiter - Himalia (11th Moon outwards from Jupiter)

Himalia as seen by Cassini–Huygens

Himalia is the largest irregular satellite of Jupiter, the fifth largest overall in size, and only the four Galilean moons are larger. Himalia is the 32th largest moon in the Solar System currently known.

Discovery

Himalia was discovered by Charles Dillon Perrine at the Lick Observatory on 3 December 1904. Himalia is Jupiter's most easily-observed small satellite.

Naming

Himalia is named after the nymph Himalia who bore three sons of Zeus (the Greek equivalent of Jupiter).

Stats

Diameter (mean): 170 km

Semi-major axis: 11,451,971 km

Orbital Period: 250.37 days

Rotation Period: 7.78 hours

Orbit

Himalia 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°. The orbital elements are as of January 2000. as they are continuously changing due to solar and planetary perturbations.

Physical characteristics

Himalia appears neutral in color (grey), like the other members of its group, similar to a C-type asteroid. Measurements by Cassini confirm a featureless spectrum, with a slight absorption at 3 μm which could indicate the presence of water.

Exploration Status

In November 2000, the Cassini spacecraft, en route 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 en route 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.

Possible Collision

The small moon S/2000 J 11, 4 kilometres in diameter, has gone missing since its discovery in 2000. One theory is that it has crashed into Himalia, creating a faint ring. This possible ring appears as a faint streak near Himalia in images from NASA's New Horizons mission to Pluto.

This suggests that Jupiter sometimes gains and loses small moons through collisions.