The waves in Saturn's rings give an accurate measure of the planet's rotation speed – ScienceDaily



The distinctive rings of Saturn were observed in unprecedented detail by NASA's Cbadini spacecraft, and scientists have now used those observations to probe the interior of the giant planet and obtain the first accurate determination of its rotation speed. The duration of a day on Saturn, according to his calculations, is 10 hours, 33 minutes and 38 seconds.

The researchers studied the wave patterns created within Saturn's rings by the planet's internal vibrations. In effect, the rings act as an extremely sensitive seismograph when responding to vibrations within the planet itself.

Similar to earth vibrations of an earthquake, Saturn responds to disturbances by vibrating at frequencies determined by its internal structure. Convection by heat in the interior is the most likely source of vibrations. These internal oscillations cause the density in any particular place within the planet to fluctuate, which causes the gravitational field outside the planet to oscillate at the same frequencies.

"The particles in the rings feel this oscillation in the gravitational field, where the oscillation resonates with the orbits of the rings, the energy accumulates and creeps like a wave," explained Christopher Mankovich, a graduate student in astronomy and astronomy. astrophysics at UC Santa Cruz. .

Mankovich is the main author of an article, published on January 17 in the Astrophysics Magazine, comparing the wave patterns in the rings with the models of the inner structure of Saturn.

Most of the waves observed in Saturn's rings are due to the gravitational effects of the moons that orbit outside the rings, said co-author Jonathan Fortney, professor of astronomy and astrophysics at UC Santa Cruz. "But some of the characteristics of the rings are due to the oscillations of the planet itself, and we can use them to understand the internal oscillations and the internal structure of the planet," he said.

Mankovich developed a set of models of Saturn's internal structure, used them to predict the frequency spectrum of Saturn's internal vibrations and compared those predictions with the waves observed by Cbadini in Saturn's C-ring. One of the main results of his badysis is the new calculation of Saturn's rotation speed, which has been surprisingly difficult to measure.

As a giant gas planet, Saturn does not have a solid surface with reference points that can be tracked as it rotates. Saturn is also unusual in having its magnetic axis aligned almost perfectly with its axis of rotation. Jupiter's magnetic axis, like that of Earth, is not aligned with its axis of rotation, which means that the magnetic pole rotates as the planet rotates, allowing astronomers to measure a periodic signal on radio waves and calculate the rotation speed.

The rotation rate of 10:33:38 determined by the Mankovich badysis is several minutes faster than the previous radiometric-based estimates of the Voyager and Cbadini spacecraft.

"We now have the duration of Saturn's day, when we thought we could not find it," said Cbadini project scientist Linda Spilker. "They used the rings to look inside Saturn's interior, and they took out this very sought-after, fundamental quality of the planet, and it's a really solid result, the rings were the answer."

The idea that the rings of Saturn could be used to study the seismology of the planet was first suggested in 1982, long before the necessary observations were possible. Co-author Mark Marley, now at the NASA Ames Research Center in Silicon Valley, subsequently developed the idea of ​​his Ph.D. The 1990 thesis showed how the calculations could be made and predicted where the characteristics would be in Saturn's rings. He also pointed out that the Cbadini mission, then in the planning stages, could make the necessary observations to prove the idea.

"Two decades later, people observed the Cbadini data and found ring characteristics at the locations of Mark's predictions," said Fortney.

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Materials provided by University of California – Santa Cruz. Original written by Tim Stephens. Note: The content can be edited by style and duration.


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