Scientists Discover How Long a Day on Saturn Lasts with New Rotation Measurement

Tracking the rotation speeds of solid planets, like the Earth and Mars, is a relatively simple process. When it comes to giant gas planets, though, this task becomes nearly impossible. Now, scientists have made the attempt to better understand the rotation of Saturn, a planet that rotates at different speeds in different parts of its sections.

Researchers have now developed a new method to determine Saturn's rotation speed. Not only that, the technique offers insight into the internal structure of the planet, its weather patterns and the way that it formed. The new findings are based on Saturn's measured gravitational field and the unique fact that its east-west axis is shorter than its north-south axis.

"In the last two decades, the standard rotation period of Saturn was accepted as that measured by Voyager 2 in the 1980s: 10 hours, 39 minutes and 22 seconds," said Ravit Helled, one of the researchers, in a news release. "But when the Cassini spacecraft arrived at Saturn 30 years later, the rotation period was measured as eight minutes longer. It was then understood that Saturn's rotation period could not be inferred from the fluctuations in radio radiation measurements linked to Saturn's magnetic field, and was in fact still unknown."

In this latest effort to understand Saturn's rotation, the researchers used a technique based on a statistical optimization method that involved several solutions. First, the solutions had to reproduce Saturn's observed properties. Then, the researchers harnessed this information to search for the rotation period on which the most solutions converged. In the end, the researchers found that Saturn's day is just 10 hours, 32 minutes and 44 seconds long.

"The rotation period of a giant planet is a fundamental physical property, and its value affects many aspects of the physics of these planets, including their interior structure and atmospheric dynamics," said Helled. "We were determined to make as few assumptions as possible to get the rotational period. If you improve your measurements of Saturn's gravitational field, you narrow the error margin."

The findings are published in the journal Nature.

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