Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Saturn ring spokes may re-appear in July, says new U. of Colorado study

17.03.2006


Voyager 2 image of Saturn ring spokes. Image courtesy NASA/JPL.


The unusual spokes that appear fleetingly on the rings of Saturn only to disappear for years at a time may become visible again by July, according to a new study spearheaded by the University of Colorado at Boulder.

The spokes, which are up to 6,000 miles long and 1,500 miles in width, were first spotted 26 years ago by the Voyager spacecraft, said CU-Boulder Mihaly Horanyi of the Laboratory for Atmospheric and Space Physics. But when the Cassini spacecraft arrived at Saturn in July of 2004, the striking radial features that cut across Saturn’s ring plane were nowhere to be found -- an event that disappointed and puzzled many scientists, he said.

The Hubble Space Telescope occasionally observed the ring spokes in the late 1990s, said Horanyi, also a professor of physics at CU-Boulder. But the spokes gradually faded, a result of Saturn’s seasonal, orbital motion and its tilted axis of rotation that altered the light-scattering geometry.



"The spokes were switched off by the time Cassini arrived," said Horanyi. "We think it is a seasonal phenomena related to the sun rising and setting over the ring plane that changes the physical environment there, making it either friendly or hostile to their formation."

A paper on the subject appears the March 17 issue of Science magazine. The paper was authored doctoral student Colin Mitchell and Horanyi of CU-Boulder’s LASP, Ove Havnes of the University of Trosmo in Norway and Carolyn Porco of the Space Science Institute of Boulder.

The spokes are made up of tiny dust particles less than a micron in width -- about 1/50th the width of a human hair -- that collect electrostatic charges in the plasma environment of the rings and become subject to electrical and magnetic forces, said Horanyi.

The right conditions cause them to gain an extra electron, allowing them to leap en masse from the surface of ring debris for brief periods, collectively forming the giant spokes that appear dark against the lit side of the rings and bright against the unlit side of the rings.

The researchers hypothesize that the conditions for the spokes to form are correlated to a decrease in the angle of the ring plane to the sun. "Because the rings are more open to the sun now than when Voyager flew by, the charging environment above the rings has prevented the formation of the spokes until very recently," the researchers wrote in Science.

Cassini first imaged a "puny version" of Saturn’s spoke rings from a distance of 98,000 miles in early September that were only about 2,200 miles in length and about 60 miles wide, said Horanyi. The team believes the spoke sighting may have been an "early bird" event.

As the ring plane angle decreases when Saturn is near its two seasonal equinoxes, the conditions appear to become more suitable for the formation of the eerie spokes, said Horanyi. Although Cassini currently is orbiting too close to the ring plane to make observations, the researchers expect the spoke activity to have returned by the time the spacecraft increases its inclination in July 2006.

Once the spokes are visible again, the research team believes there will be spoke activity for about eight years, based on fact that it takes Saturn about 30-Earth-years to complete one orbit around the sun, said Horanyi. The eight-year period should be followed by about six to seven years of a spoke hiatus, he said.

The dust grains levitated by plasma during spoke-forming periods are probably hovering less than 50 miles above the rings themselves and they scatter light from the sun differently than do the rings themselves, he said.

But there are still many questions about the spokes, said Horanyi. "We don’t know if they form by rapidly expanding, or if they form all at once," he said. During the Voyager mission, they were absent during one observation, but fully developed in a follow-up observation made just five minutes later, he said.

This is a weird phenomena we don’t have the full story on yet," said Horanyi.

Mihaly Horanyi | EurekAlert!
Further information:
http://www.colorado.edu

More articles from Physics and Astronomy:

nachricht Study offers new theoretical approach to describing non-equilibrium phase transitions
27.04.2017 | DOE/Argonne National Laboratory

nachricht SwRI-led team discovers lull in Mars' giant impact history
26.04.2017 | Southwest Research Institute

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

Bare bones: Making bones transparent

27.04.2017 | Life Sciences

Study offers new theoretical approach to describing non-equilibrium phase transitions

27.04.2017 | Physics and Astronomy

From volcano's slope, NASA instrument looks sky high and to the future

27.04.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>