Jarnsaxa is a member of the Norse group of moons, which orbit Saturn at mean distances ranging from 12 to 24 million km, at inclinations between 136° and 176° from the plane of Saturn's equator, and with eccentricities between 0.12 and 0.77. (A satellite's eccentricity is a number between 0 and 1 which describes the shape of the orbit. The closer to 0, the more circular it is; the closer to 1, the more elongated.)
The Norse moons all have retrograde orbits (they travel around Saturn in the opposite direction from the planet's rotation). That and their deviations from circular orbits and from the plane of Saturn's equator classify them as "irregular" satellites. Like Saturn's other irregular moons, they are thought to be objects that were captured by Saturn's gravity, rather than having accreted from the dusty disk that surrounded the newly formed planet as the regular satellites are thought to have done.
Unlike the Gallic and Inuit groups of Saturn's moons, the wide range of distances, inclinations and eccentricities among moons in the Norse group suggest that they are not the pieces of a single original object that shattered in a collision, but they may be the pieces of several such "original" objects.
Jarnsaxa has a mean radius of about 3.0 km, assuming an albedo of 0.04. It orbits Saturn at an inclination of about 163° and an eccentricity of about 0.2. At a mean distance of 19.3 million km from Saturn, the satellite takes about 1007 Earth days to complete one orbit.
Jarnsaxa was discovered on 6 March 2006 by Scott S. Sheppard, David C. Jewitt and Jan Kleyna using the Subaru 8.3-m reflector telescope on Mauna Kea, Hawaii.
How Jarnsaxa Got its Name:
Originally called S/2006 S6, Jarnsaxa was named for one of the nine giantesses in Norse mythology who gave birth to Heimdall, the guard of the rainbow bridge that links our world to Asgard, home of the gods.