Astronomy Cast Ep. 195: Planetary Rings

Saturn's rings

Saturn is best known for its rings. This huge and beautiful ring system is easy to spot in even the smallest backyard telescope, so you can imagine they were a surprise when Galileo first noticed them. But astronomers have gone on to find rings around the other gas giant worlds in the Solar System – the differences are surprising.

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Astronomy With the Unaided Eye shownotes and transcript.

6 Replies to “Astronomy Cast Ep. 195: Planetary Rings”

  1. A fascinating podcast! Thanks for the time and effort you put into sharing your creations! It is fascinating that our outer Gas Giants all have rings and multitudes of icy satellites!

    I would like to add something I found later…. this excerpt from SATURN: MAGNETIC FIELD AND MAGNETOSPHERE


    Originally published in
    Encyclopedia of Planetary Sciences, edited by J. H. Shirley and R. W. Fainbridge,
    718-719, Chapman and Hall, New York, 1997.


    Saturn also has an immense magnetosphere whose linear dimension is about one-fifth that of the Jovian magnetosphere. This magnetosphere is more similar to the terrestrial magnetospheres than that of Jupiter. The magnetosphere traps radiation belt particles, and these particles reach levels similar to those of the terrestrial magnetosphere. On their inner edge the radiation belts are terminated by the main (A, B and C) rings of Saturn, which absorb any particles that encounter them. The radiation belt particles also are absorbed if they collide with one of the moons. Hence there are local minima in the energetic particle fluxes at each of the moons. Unlike Jupiter, but like the Earth, there is no internal energy and mass source deep in the Saturnian magnetosphere. However Titan, which orbits just inside the average location of the magnetopause, in the far reaches of the magnetosphere, has an interesting interaction.

    Titan (q.v.) is the most gas-rich moon in the solar system, having an atmospheric mass per unit area much greater than even that of the Earth. At its upper levels this atmosphere becomes ionized through charge exchange, impact ionization and photoionization. This newly created plasma adds mass to the magnetospheric plasma, which attempts to circulate in the Saturnian magnetosphere at a velocity similar to that needed to remain stationary with respect to the rotating planet. Since this velocity is much faster than the orbital velocity of Titan, the added mass slows the ‘corotating’ magnetospheric plasma. The magnetic field of the planet that is effectively frozen to the magnetospheric plasma is then stretched and draped about the planet, forming a slingshot which accelerates the added mass up to corotational speeds. Thus the interaction between the Saturn magnetosphere and the Titan atmosphere resembles the interaction of the solar wind with comets and with Venus (Kivelson and Russell, 1983).

    The Saturn magnetosphere, like the other planetary magnetospheres, is an efficient deflector of the solar wind. The solar wind at Saturn flows more rapidly with respect to the velocity of compressional waves than at Jupiter and the terrestrial planets. Thus the shock that forms at Saturn is very intense. Ironically this strength may weaken at least one form of coupling of the solar wind with the magnetosphere, that due to reconnection. However, some aspects of the interaction of the solar wind plasma should be much stronger than at Jupiter or at Earth because of the increased strength of the shock and the scale size of the interaction, which can accelerate charged particles to very high levels.

    Saturn is also expected (like Jupiter) to have a very large tail, possibly one that could be dynamic like that of the Earth. However, observations of the tail are quite limited and we must wait until the Cassini mission (q.v.) in the early 21st century for further studies of the magnetic field, magnetosphere and magnetotail, and the answers to many of the questions that the Pioneer and Voyager data have generated.

  2. I like!

    “New Recipe For Oxygen On Icy Moons”

    “Lightning Holds Fingerprint of Antimatter”

    “Graphene under stress creates gigantic pseudo-magnetic fields”

    Could it be that Saturn is constantly making its own rings and icy satellites with a combination of these process’? Have we ‘overlooked’ something?

  3. The second link was added because it refers to a possible high energy source for fusion processes.

    The third link about Graphene’s unusual properties begs the question of whether or not similar elemental magnetic properties may occur deep in the atmosphere of Saturn?

    The MOST unusual comment in the first post refers to: “On their inner edge the radiation belts are terminated by the main (A, B and C) rings of Saturn, which absorb any particles that encounter them.”

    So the rings themselves absorb hot particles… Hmmm….

  4. A recent discovery by the Herschel infrared space observatory has discovered that ultraviolet starlight is the key ingredient for making water in space.

    Could not this same process be at work at Saturn?

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