Notes

https://bgr.com/2019/01/21/saturn-day-length-astronomy-space-cassini/
At last, scientists have finally determined the exact length of a day on Saturn. You may think its easy to find out how long a day is on a planet, but you're wrong. Normally, you pick a landmark and wait for it to reach the exact same point twice in its rotation and you have your answer. But, Saturn doesn’t have any easily visible landmarks to track, and its gassy atmosphere doesn’t offer many hints as to how fast it’s actually rotating. On top of that, its magnetic field also hides the speed at which the body spins. Researchers were at a loss as to how to track the planet’s rotation. But, a graduate student at UC Santa Cruz cracked the code and discovered that Cassini’s observations of Saturn’s delicate ring structure held the key to determining the rate at which Saturn itself rotates. Using this trick, it was found out that a single day on Saturn lasts 10 hours, 33 minutes, and 38 seconds. The past estimate was 10 hours, 39 minutes, and 23 seconds. This makes the new estimate the most accurate measurement to date of Saturn.