Gerd (moon)

Gerd is a small, irregular moon of Saturn. It is a member of the Norse group of irregular satellites.

Discovery and Naming

Gerd was discovered on January 5, 2006, by Scott S. Sheppard, David C. Jewitt, Jan Kleyna, and Brian G. Marsden, using observations taken with the Subaru Telescope on Mauna Kea. It was given the provisional designation S/2006 S 9. In April 2007, it was officially named after Gerðr, a goddess in Norse mythology, a giantess who became the wife of the god Freyr.

Orbital Characteristics

Gerd orbits Saturn at an average distance of about 23.0 million kilometers. It has a highly inclined and eccentric orbit. Its orbital inclination is approximately 173° to the ecliptic (151° to Saturn's equator), which means it is retrograde, orbiting Saturn in the opposite direction to the planet's rotation. Its orbital period is approximately 1298 days.

Physical Characteristics

Gerd is estimated to be approximately 6 kilometers in diameter, assuming an albedo (reflectivity) of 0.06. Due to its small size and great distance from Earth, little is known about its surface composition or other physical characteristics. It is likely primarily composed of rock and ice.

Classification

As a member of the Norse group, Gerd shares similar orbital characteristics with other Saturnian irregular satellites like Skathi, Narvi, and Bergelmir. The Norse group satellites are believed to have a common origin in the breakup of a larger parent body that was captured by Saturn's gravity. This breakup likely occurred after the initial capture event.