page_title: Rings of Saturn
section_title: Keeler Gap
hierarchical_section_title: Rings of Saturn / A Ring / Keeler Gap
caption_attribution_description: Uploader's notes: the original NASA image has been modified by stretching by a factor of 2 in both dimensions, sharpening and converting from TIFF to JPEG format. Original caption released with image: Daphnis drifts through the Keeler gap, at the center of its entourage of waves. The little moon (7 kilometers, or 4.3 miles across) draws material in the Keeler gap (42 kilometers, or 26 miles wide) into these now familiar edge waves as it orbits Saturn. This view looks toward the lit side of the rings from about 25 degrees below the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Oct. 27, 2006 at a distance of approximately 325,000 kilometers (202,000 miles) from Daphnis and at a Sun-Daphnis-spacecraft, or phase, angle of 36 degrees. Image scale is 2 kilometers (1 mile) per pixel. 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. For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov/home/index.cfm. The Cassini imaging team homepage is at http://ciclops.org.
context_page_description: The rings of Saturn are the most extensive ring system of any planet in the Solar System. They consist of countless small particles, ranging in size from micrometers to meters, that orbit about Saturn. The ring particles are made almost entirely of water ice, with a trace component of rocky material. There is still no consensus as to their mechanism of formation. Although theoretical models indicated that the rings were likely to have formed early in the Solar System's history, new data from Cassini suggest they formed relatively late.
  Although reflection from the rings increases Saturn's brightness, they are not visible from Earth with unaided vision. In 1610, the year after Galileo Galilei turned a telescope to the sky, he became the first person to observe Saturn's rings, though he could not see them well enough to discern their true nature. In 1655, Christiaan Huygens was the first person to describe them as a disk surrounding Saturn.
context_section_description: The Keeler Gap is a 42-km-wide gap in the A ring, approximately 250 km from the ring's outer edge. The small moon Daphnis, discovered 1 May 2005, orbits within it, keeping it clear. The moon's passage induces waves in the edges of the gap (this is also influenced by its slight orbital eccentricity). Because the orbit of Daphnis is slightly inclined to the ring plane, the waves have a component that is perpendicular to the ring plane, reaching a distance of 1500 m "above" the plane.
  The Keeler gap was discovered by Voyager, and named in honor of the astronomer James Edward Keeler. Keeler had in turn discovered and named the Encke Gap in honor of Johann Encke.
caption: Waves in the Keeler gap edges induced by the orbital motion of Daphnis (see also a stretched closeup view in the gallery).
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