Much narrower is the hairlike Encke Division
barely inside the A ring's outer edge.
Similar brightness variations appear in the F-ring of Saturn and a pair of narrow rings in Saturn's Encke division
. Some planetary scientists suggest the arcs consist of fragments of former moons ground up by collissions with other moons (SN: 8/5/89, p.87).
Atlas orbits just outside Saturn's A ring, and Pan orbits inside it (in the Encke Division
(There are signs of a "partial" ring in Voyager photos of the Saturn ring system's Encke division
, Brahic notes.) Could part of it be "kinked" out of the way or otherwise distorted by the presence of satellites or other factors?
Two moons, each several kilometers wide, orbit inside gaps in the outer A ring: Pan in the 320-km-wide Encke Division
and Daphnis in the 35-km-wide Keeler Gap.
Just inside the A ring's outer edge is the extremely thin Encke Division
or Keeler Gap (usage varies)--an extreme test for any telescope.
Since the Encke Division
in Saturn's rings is a linear feature, some people think that it is easier to resolve.
The lunar-orbit-insertion-burn segment of the diagram showing how Apollo astronauts got to the Moon has problems, the Encke Division
in Saturn's rings is mislabeled, an illustration of the Sun erroneously shows sunspots at its poles, the descriptions and illustrations of a reflector and a catadioptric telescope are incorrectly paired, the giant elliptical galaxy M87 is misidentified in several places as M82, and a diagram explaining the seasons is exactly backward.
A second mechanism involves small moons embedded within gaps, such as the tiny moon Pan that clears out the Encke Division
. Porco and her colleagues are excited about this possibility.
As fellow observer Jeff Schroeder explained, this feature is often mistaken for the Encke Division
, which is actually much closer to the ring's outer edge.
(At its outer edge is the extremely narrow Encke Division
, which is almost never resolved separately.) Last year, on a night when the seeing was so steady I could use 450x on my 12.5-inch reflector, I observed the Encke Minimum well for the first time -- a complex blur of threadlike details during moments when the air was perfectly steady.
Even though the rings were nearly edge on, I could make out the Cassini and Encke divisions
. On the planet itself, I could follow the belt system all the way to the olivine polar regions.