Bestla was discovered on Dec. 12, 2004, one of 12 Saturnian moons found that day by Scott S. Sheppard, David C. Jewitt, and Jan T. Kleyna, using wide-field camera on the Subaru 8.3-m reflector telescope on Mauna Kea, Hawaii. Brian Marsden computed the orbital elements.
Bestla has a mean radius of 2.2 miles (3.5 km), assuming an albedo (a measure of how reflective the surface is) of 0.04. It orbits Saturn at an inclination of about 142 degrees and an eccentricity of about 0.5. At a mean distance of 12.6 million miles (20.3 million km) from Saturn, the moon takes about 1,087 Earth days to complete one orbit.
Bestla 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. Bestla and the other Norse moons also have eccentric orbits, meaning they are more elongated than circular.
Like Saturn's other irregular moons, Bestla 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. Bestla appears to be a member of a subgroup with Narvi.
How Bestla Got its Name
Originally called S/2004 S18, Bestla is named for a giantess and the mother of Odin, who is the supreme god in Norse mythology.