<P> Johann Encke himself did not observe this gap; it was named in honour of his ring observations . The gap itself was discovered by James Edward Keeler in 1888 . The second major gap in the A ring, discovered by Voyager, was named the Keeler Gap in his honor . </P> <P> The Encke Gap is a gap because it is entirely within the A Ring . There was some ambiguity between the terms gap and division until the IAU clarified the definitions in 2008; before that, the separation was sometimes called the "Encke Division". </P> <P> 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 . </P> <P> 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 . </P>

How is the cassini division created and maintained in saturn's rings