Shepherd Moons & Planetary Rings. Saturn's Ring Structure Prior to the space program we thought Saturn had only a few rings.
The Voyager mission to Saturn sent back pictures of the rings that revealed tens of thousands of individual rings. Scientists scrambled to solve the puzzle of this structure. Two of the most likely causes of Saturn's ring structure are resonances with Saturn's larger moons and small shepherd moons. Shepherd Moons Sometimes two small moons in the rings act together as shepherd (sometimes called guardian moons or satellites) moons. How? There are two keys to understanding this counterintuitive behavior.
The second key is understanding the energy of an orbit. What about the total energy, which is the sum of the potential and kinetic energy? A shepherd moon orbiting just outside a narrow ring will orbit Saturn more slowly than the individual particles composing the ring. Further Reading Chaisson, E, and McMillan, S. Fowles, G.R., and Cassidy, G.L., Analytical Mechanics 6th ed., Saunders, 2004. Shepherd Moons of Saturn. Pandora. This image shows three of Saturn's small moons and a portion of its rings (left).
The two shepherd moons, Prometheus and Pandora, guide particles in the F ring into a narrow band. Another small moon, Epimetheus, can be seen in the upper right corner of the image. This image was taken by the Cassini spacecraft on May 1, 2004 when Cassini was 31.4 million km (19.5 million miles) from Saturn. Click on image for full size Image courtesy NASA/JPL/Space Science Institute. Pandora is a small moon of Saturn. Pandora's name comes from Greek mythology. Pandora and Prometheus, another small moon of Saturn, are known as shepherd satellites. Pandora is not round, but is more of a "potato-shaped" moon. Shop Windows to the Universe Science Store! Our online store includes issues of NESTA's quarterly journal, The Earth Scientist, full of classroom activities on different topics in Earth and space science, ranging from seismology, rocks and minerals, oceanography, and Earth system science to astronomy!
Shepherd Moons by ~AkenBosch on deviantART. The_cross_section_of_the_rocky_ring_system_of_a_fictional_planet.1920x1200.c9facb34. Crossed rings planet. Index.php?PHPSESSID=47526a7017a563b4681bb6c2cd0d8ef8&action=dlattach;topic=3673. Exorings Could Soon Be Detected Around Exoplanets. Some of the most interesting directions of research in astronomy include the discovery of extrasolar moons.
But scientists say that finding extrasolar rings may also prove helpful in our quest for potentially-habitable ecosystems in space. Astronomers know that exorings exist around distant worlds simply because gas giants have been identified in other star systems. Additionally, all planetary formation mechanisms are the same throughout the Universe, so the existence of gas giants implies dust and ice rings are present, too. Experts proposed looking for exorings as far back as 2004, but observations technologies at the time were not nearly as advanced as they are today, so the quest was doomed from the start. However, theoreticians did provide some insight into how such observations could be conducted. Even so, exorings could theoretically be detected only if they are placed face-on, rather than edge-on.
This would make it impossible for even Kepler to see them. [1104.3863] Warm Saturns: On the Nature of Rings around Extrasolar Planets that Reside Inside the Ice Line. 1111.5599v1.