S/2004 S13

S/2004 S13 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.

S/2004 S13 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 169 degrees and an eccentricity of about 0.3. At a mean distance of 11.4 million miles (18.4 million kilometers) from Saturn, the satellite takes about 934 Earth days to complete one orbit.

Yet to be named S/2004 S13 is a member of the Norse group of moons. These "irregular" satellites have retrograde orbits around Saturn -- traveling around in the opposite direction from the planet's rotation. S/2004 S13 and the other Norse moons also have eccentric orbits, meaning they are more elongated than circular.

Like Saturn's other irregular moons, S/2004 S13 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 satellites are thought to have done.

S/2004 S13 was so designated because it is a satellite (S) that was discovered in 2004, and was the 13th satellite of Saturn (S) to be found that year.