12.5 Planetary rings  (Page 7/21)

Key concepts and summary

Rings are composed of vast numbers of individual particles orbiting so close to a planet that its gravitational forces could have broken larger pieces apart or kept small pieces from gathering together. Saturn’s rings are broad, flat, and nearly continuous, except for a handful of gaps. The particles are mostly water ice, with typical dimensions of a few centimeters. One Saturn moon, Enceladus, is today erupting geysers of water to maintain the tenuous E Ring, which is composed of very small ice crystals. The rings of Uranus are narrow ribbons separated by wide gaps and contain much less mass. Neptune’s rings are similar but contain even less material. Much of the complex structure of the rings is due to waves and resonances induced by moons within the rings or orbiting outside them. The origin and age of each of these ring systems is still a mystery.

For further exploration

Articles

Moons

Carroll, M. “Titan: What We’ve Learned about a Strange New World.” Astronomy (March 2010): 30. Nice review of Cassini mission results.

Elliot, J. “The Warming Wisps of Triton.” Sky&Telescope (February 1999): 42. About Neptune’s intriguing moon.

Hayes, A., “Secrets from Titan’s Seas.” Astronomy (October 2015): 24. Good review of what we now know and what puzzles us about the hydrocarbon lakes of Titan.

Jewitt, D., et al. “The Strangest Satellites in the Solar System.” Scientific American (August 2006): 40. Small irregular moons in the outer solar system.

Lakdawalla, E. “Ice Worlds of the Ringed Planet.” Sky&Telescope (June 2009): 27. On the Cassini mission exploration of Enceladus, Iapetus, and other moons.

Mackenzie, D. “Is There Life under the Ice?” Astronomy (August 2001): 32. On future exploration of Europa.

Robertson, D. “Where Goes the Rain?” Sky&Telescope (March 2013): 26. About the methane weather cycle on Titan and what Cassini experiments are telling us.

Scharf, C. “A Universe of Dark Oceans.” Sky&Telescope (December 2014): 20. Subsurface oceans on Europa, Ganymede, Enceladus, and Titan.

Showalter, M. “How to Catch a Moon (or Two) of Pluto.” Astronomy Beat (December 2012): http://www.astrosociety.org/wp-content/uploads/2013/02/ab2012-106.pdf. On the discovery of small moons around Pluto, written by the person who discovered two of them.

Spencer, J. “Galileo’s Closest Look at Io.” Sky&Telescope (May 2001): 40.

Talcott, R. “Cassini Flies through Enceladus’ Geysers.” Astronomy (March 2009): 32.

Zimmerman, R. “Does Methane Flow on Titan?” Astronomy (February 2014): 22. Ideas about lakes, channels, and rain.

Pluto

Stern, A. “Pluto: Up Close and Personal.” Astronomy (July 2015): 22. Good summary of the history of understanding Pluto and our current knowledge on the eve of the New Horizons encounter.

Stern, A. “The Pluto System Explored.” Astronomy (November 2015): 24. Fine review of what the team learned from the first few data downloads from New Horizons.

Tombaugh, C. “How I Found Pluto” Astronomy Beat (May 2009): http://astrosociety.org/wp-content/uploads/2013/02/ab2009-23.pdf.

Rings

Beatty, J. “Saturn’s Amazing Rings.” Sky&Telescope (May 2013): 18. Good 7-page summary of what we know.