열람 Encke Gap
The Encke Gap is a 325-kilometre-wide gap within the A Ring, centered at a distance of 133,590 kilometers from Saturn’s center.[35] It is caused by the presence of the small moon Pan,[36] which orbits within it. Images from the Cassini probe have shown that there are at least three thin, knotted ringlets within the gap.[24] Spiral density waves visible on both sides of it are induced by resonances with nearby moons exterior to the rings, while Pan induces an additional set of spiraling wakes (see image in gallery).[24]
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.[37] The second major gap in the A Ring, discovered by Voyager, was named the Keeler Gap in his honor.[38]
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; prior to that, the separation was sometimes called the “Encke Division”.[citation needed]