S/2004 S7

S/2004 S7 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.

Not yet officially named, S/2004 S7 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 0.5. At a mean distance of 13 million miles (21 million kilometers) from Saturn, the satellite takes about 1,140 Earth days to complete one orbit.

S/2004 S7 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 S7 and the other Norse moons also have eccentric orbits, meaning they are more elongated than circular.

Like Saturn's other irregular moons, S/2004 S7 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 S7 was so designated because it is a satellite (S) that was discovered in 2004, and was the 7th satellite of Saturn (S) to be found that year.