Hati 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 degrees 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.
Hati has a mean radius of about 3.0 km, assuming an albedo of 0.04. It orbits Saturn at an inclination of about 165 degrees and an eccentricity of about 0.4. At a mean distance of 19.8 million km from Saturn, the satellite takes about 1,039 Earth days to complete one orbit.
Discovery:
Hati was discovered on 12 December 2004, one of 12 Saturnian moons found that day by Scott S. Sheppard, David L. Jewitt and Jan T. Kleyna, using a wide-field camera on the Subaru 8.2-m reflector telescope on Mauna Kea, Hawaii. Brian Marsden computed the orbital elements.
How Hati Got its Name:
Originally called S/2004 S14, Hati was named for a giant wolf in Norse mythology who pursues the Moon (that is, the Moon chariot and the boy who drives it -- see Mundilfari for an explanation) across the sky. According to the mythology, Hati is destined to catch and devour them at the doomsday time known as Ragnarok.
