Hati was discovered on Dec. 12, 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.
Hati has a mean radius of 1.9 miles (3 kilometers), assuming an albedo (a measure of how reflective the surface is) 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 12.3 million miles (19.8 million kilometers) from Saturn, the moon takes about 1,039 Earth days to complete one orbit. Its rotational period is just 5.5 hours, the fastest known rotation of all of Saturn's moons.
Hati is a member of the Norse group of moons. These "irregular" moons have retrograde orbits around Saturn—traveling around in the opposite direction from the planet's rotation. Hati and the other Norse moons also have eccentric orbits, meaning they are more elongated than circular.
Like Saturn's other irregular moons, Hati is thought to be an object that was captured by Saturn's gravity, rather than having accreted from the dusty disk that surrounded the newly formed planet as the regular moons are thought to have done.
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.