Author: Lisa Grossman / Source: Science News
You can’t tell how fast Saturn is spinning by watching the clouds swirling at its surface. But ripples in its rings reveal how fast the planet rotates: Its day flies by in 10 hours, 33 minutes and 38 seconds.
“That’s a really fast clip,” says astronomer Christopher Mankovich of the University of California, Santa Cruz, who reports the rotation rate in the Astrophysical Journal on January 17. Saturn, with a radius of about 58,000 kilometers, is about nine times the size of Earth yet its day is less than half as long.
Scientists previously estimated possible lengths for a Saturnian day using radio measurements from the Voyager spacecraft in the 1980s and from the Cassini orbiter in the 2000s. But those estimates, while in the same ballpark as the new one, varied by about 20 minutes.
In 1993, astronomers Mark Marley and Carolyn Porco, who later led Cassini’s imaging team, realized that Saturn’s seismic activity changes the…
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