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Wendy Darling famously helped Peter Pan catch his shadow, and now Cassini captures the shadow of another Pan: Saturn’s 30-kilometer (19-mile) wide moon inhabiting the Encke Gap.
In the center of this image, the shadow of Pan is a short streak thrown over the edge of the A ring where Pan travels its path through the Encke Gap. A second version of this image has been included to focus on Pan’s shadow. The image has been scaled to three times its original size and cropped as shown in Fig. 1.
One of the happy results of Saturn’s 29-year revolution around the sun is the changing elevation of the sun seen from the planet, and the changing elevation of the shadows of the rings and moons that the sun’s apparent motion brings.
As Saturn approaches equinox, the angle at which the ringplane is inclined away from the sun will continue to decrease until August 2009, when equinox will bring about an alignment of the plane containing the rings with the rays of the sun. Only around the time of equinox is a moon’s shadow cast on the rings rather than the planet.
Between now and equinox in August, the shadows cast by the moons on the rings will grow longer with time.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.
Image Credit: NASA/JPL/Space Science Institute