Puzzle for our Solar System – How Long is Saturn's Day? – is resolved with a new data analysis. This figure was difficult to calculate because the gas giant has no solid surface, so there are no landmarks that can be traced as the planet rotates. In addition, the magnetic field makes it difficult to see the speed of rotation.
But now NASA scientists have used data from the Cassini spacecraft to determine the final answer: Saturn's day is ten hours, 33 minutes and 38 seconds. long. The new day of 10:33:38 is slightly shorter than the previous estimates, such as the estimate of 10:39:22 from 1981 based on Voyager's magnetic field data.
The new figure is calculated by looking at the rings of Saturn, for which Cassini collected very detailed data during his mission from the start of 1997 to his eventual destruction in the atmosphere of the planet 2017. During its orbit from Saturn from 2004 onwards the ship collects high-resolution images on the planet and data on its ice rocky rings. Then these data were used by the aspirant Christopher Mankovich to study the wave patterns in the rings.
Mankovich finds that the rings acted as a type of seismometer, corresponding to the vibrations that occurred within the planet. When the interior of the planet vibrates and earthquakes occur, vibration frequencies cause changes in the planet's gravitational field, and these variations are transmitted to the rings. "The particles in the rings can not help, but they feel these oscillations in the gravitational field," Mankovich said in a statement. "At certain points in the rings, these vibrations capture the particles of the ring at exactly the right time in their orbits to increase the energy gradually, and that energy is carried as a wave."
This means scientists can monitor the movements from the inside of the planet, and from this tracking they can see the rotation of the planet. This allows them to calculate the exact duration of Saturn's day. "Researchers used waves in the rings to enter Saturn's interior, and took out this long-sought, fundamental feature of the planet. And this is a really solid result, "said Cassini project scientist Linda Spielker in the same statement. "On rings is responsible."
The document is available in the Physics Archive arXiv.