Saturn’s rotation period
A new method to determine the rotation period of Saturn was presented in an article in the latest issue of Nature. To put it in place, a group of researchers led by Ravit Helled, at Tel Aviv University made possible the measurements of Saturn’s rotation period.
How long is a day on Saturn? A little less than 11 hours, that is for sure. But to scientists, you know, they do not like to settle for information as approximate and for years, studying the ringed planet, they are trying to obtain accurate measurements of its rotation period. Not such an insignificant information or pure curiosity to know precisely this value but this result can help them to better understand other aspects of the planet, as its structure and internal composition. The task, however, is somewhat difficult because Saturn is a gaseous planet that does not have detectable solid structures, in contrast to the Earth or Mars, for example, which may be taken as an easy reference for timing how long the celestial body completes a full rotation around its axis.
But now a new method to determine the rotation period of Saturn comes from the pages of the latest issue of Nature. To put it in place, a group of researchers led by Ravit Helled, at Tel Aviv University made possible the results. The new technique, which is based on measurements of the gravitational field of Saturn and its different configurations along the North-South and East-West, has allowed the construction of a Saturn day that lasts 10 hours, 32 minutes and 44 seconds.
“Over the past twenty years, the period of rotation of Saturn commonly accepted as standard has been measured by Voyager 2 in the 80s of last century: 10 hours and 39 minutes, and 22 seconds,” says Helled. “But when the Cassini spacecraft arrived at Saturn 30 years later, the rotation period calculated from its observations rose by eight minutes. We understood as that this value could not be deduced from measurements of the intensity fluctuations of radio waves associated with Saturn’s magnetic field, and thus remained virtually unknown. Of course, in recent years, there have been several theoretical attempts to find an answer to this enigma. We propose our own, which is based on the shape and the gravitational field of the planet. By observing the global properties, we determined the rotation period. ”
The proposed method is based on statistical optimization processes involving different solutions. First, these solutions had to be able to reproduce as accurately as possible the properties of observation of Saturn, in particular its mass and its gravitational field. The best among those obtained were finally used to derive the rotation period. As a check, the team applied the method to calculate the rotation period of Jupiter and the results are in good agreement with those obtained with other techniques, known having precision. The next step is to extend this method to other gas planets of the Solar System, Uranus and Neptune. And maybe even beyond, up to the gas planets that orbit around other stars.