Kalyke

Kalyke was discovered on Nov. 23, 2000 by Scott S. Sheppard, David C. Jewitt, Yanga R. Fernandez, and Eugene Magnier at the Mauna Kea Observatory in Hawaii.

Kalyke is a member of the Carme group, a family of Jovian satellites which have similar orbits and appearance and are therefore thought to have a common origin. The group probably began as a D-type asteroid (possibly from the Hilda family or the Jupiter Trojans) that suffered a collision, which broke off a number of pieces, either before or after being captured by Jupiter's gravity. The largest remaining chunk (still retaining 99% of the group's mass) was named "Carme," and the smaller pieces became the other 16 moons in the Carme group.

All of the Carme moons are retrograde, which means that they orbit Jupiter in the opposite direction from the planet's rotation. Their orbits are also eccentric (elliptical rather than circular) and highly inclined with respect to Jupiter's equatorial plane. They all are very similar in color – light red – except for Kalyke, which is considerably redder than the others. All of these characteristics support the idea that the Carme satellites began as a captured asteroid, rather than forming as part of the original Jupiter system. None of the Carme members is massive enough to pull itself into a sphere, so they are probably all irregularly shaped.

Kalyke has a mean radius of about 1.6 miles (2.6 kilometers). At a mean distance of about 14.6 million miles (23.5 million kilometers) from Jupiter, the satellite takes about 742 Earth days to complete one orbit.

Originally called S/2000 J2, Kalyke was named for the mother of Endymion by Zeus (the Greek equivalent of the Roman god Jupiter) according to some accounts in Greek mythology. Some sources say that Zeus offered Endymion anything he wished and he chose eternal sleep in which he would retain his youthful beauty forever. By other accounts, Zeus condemned him to everlasting sleep as punishment for an attempted sexual relationship with Zeus' wife, Hera. Yet another version of the myth has it that he was put to sleep by Selene, goddess of the moon, who loved him, visited him every night and bore him 50 daughters.

A name ending in "e" was chosen for this moon in accordance with the International Astronomical Union's policy for designating outer moons with retrograde orbits.