13th Largest Moon of Jupiter - Lysithea (12th Moon outwards from Jupiter)

Lysithea is a prograde irregular satellite of Jupiter.

Lysithea is the 13th largest moon of Jupiter and 75th largest moon in the Solar System currently known.

Discovery

Lysithea was discovered by Seth Barnes Nicholson on July 6, 1938 with the 100-inch (2.5 m) Hooker telescope at the Mount Wilson Observatory.

Naming

Lysithea the moon is named after the mythological Lysithea, daughter of Oceanus and one of Zeus' lovers.

In Greek mythology, Lysithea was a daughter of Oceanus and one of Zeus' lovers.

Lysithea didn't receive its present name until 1975; before then, it was simply known as Jupiter X. Or it was sometimes called "Demeter" from 1955 to 1975.

In Greek mythology, Demeter is the goddess of the harvest, who presided over grains and the fertility of the earth.

A name ending in "a" was chosen for this moon in keeping with the International Astronomical Union's policy for designating Jupiter's outer moons which have prograde orbits (orbiting in the same direction as Jupiter's rotation).

Stats

Diameter (mean): 36 km

Semi-major axis: 11,740,560 km

Orbital Period: 259.2 day

Orbit

Lysithea belongs to the Himalia group, a family of Jovian satellites which have similar orbits and appearance, and are therefore thought to have a common origin. Its orbital elements are as of January 2000. They are continuously changing due to solar and planetary perturbations.

Physical characteristics

Lysithea has an estimated diameter of 36 km (assuming an albedo of 0.04).

Lysithea may be a chunk of an asteroid (a C- or D-class asteroid, judging by the fact that it reflects only about 4% of the light it receives), which was broken apart in a collision either before or after being captured by Jupiter's gravity.

In this scenario, the other pieces became the other moons in the Himalia group: Leda, Himalia (the largest) and Elara. A fifth moon, called S/2000 J11, only about 2 km in radius, was considered a candidate for this group. However, it was lost before its orbit could be definitively determined.

S/2000 J11 may have crashed into Himalia, reuniting two pieces of the former asteroid, and perhaps creating a faint temporary ring of Jupiter near the orbit of Himalia.