Greip was discovered on March 6, 2006 by Scott S. Sheppard, David C. Jewitt and Jan T. Kleyna using the Subaru 8.3-m reflector telescope on Mauna Kea, Hawaii.
Greip 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 173 degrees and an eccentricity of about 0.3. At a mean distance of 11.5 million miles (18.4 million kilometers) from Saturn, the moon takes about 936 Earth days to complete one orbit.
Greip 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. Greip and the other Norse moons also have eccentric orbits, meaning they are more elongated than circular.
Like Saturn's other irregular moons, Greip 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 Greip Got its Name
Originally called S/2006 S4, Greip was named for one of the nine giantesses who gave birth to Heimdall, the guard of the rainbow bridge that links our world to Asgard, home of the Norse gods.