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Herse: Overview
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Herse 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.

Herse has a mean radius of about one kilometer. At a mean distance of about 23.4 million km from Jupiter, the satellite takes more than 734 Earth days to complete one orbit.

Discovery:
Herse was discovered on 27 February 2003 by Brett J. Gladman, John J. Kavelaars, Jean-Marc Petit, and Lynne Allen.

How Herse Got its Name:
Originally called S/2003 J17, Herse was named for a daughter of Selene (goddess of the moon) and Zeus, the Greek equivalent of the Roman god Jupiter.

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

Just the Facts
Orbit Size (semi-major axis):  14,543,193 miles
Mean Radius:  0.6 miles
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Last Updated: 9 Mar 2011