The riddle of the rotation of Saturn

In our century, when spacecraft along and across the spaces of the solar system, it may seem quite strange that we still unknown the exact period of the rotation of Saturn. However, if you think about it, the situation is non -trivial: how to determine the period of the axial rotation of the planet that has no solid surface (or at least it is not visible)? In the case of Jupiter, the magnetic field helps: the Jupiterian magnetic dipole is tilted to the axis of rotation of the planet, and the period of its axial rotation can be determined by measuring periodic variations of the magnetic field in the vicinity of Jupiter. With Saturn, this method works much worse, since the axis of its magnetic field practically coincides with the axis of rotation. Nevertheless, according to the variations in the radio emission of the magnetosphere of Saturn, measured using the Voyagers in the early 1980s, the rotation period was established-about 10 hours 39 minutes. Similar dimensions, made in 2003-2004 with the help of the Kassini spacecraft, gave significantly more - 10 hours 45 minutes. Such a discrepancy can be explained by the fact that according to the magnetic field, the speed of rotation of the magnetic field, not the planet, is determined, and the magnetic field can shift inside Saturn. Therefore, to determine the speed of rotation of the planet, it is advisable to attract data not only by the magnetic field.

In 2007, John Anderson and Gerald Schubert tried to evaluate the speed of Saturn’s rotation using his form and gravitational field received using Cassini and received an estimate of 10 hours 32 minutes 35 seconds. And in March 2015, a new assessment was published ( http://adsabs.harvard.edu/abs/2015natur.520..202h ).

Ravit Helled (Israel) with colleagues also used data on the gravitational field of Saturn and tried to combine it with data on the polar compression of the planet, as well as restrictions on its internal structure. For verification, they applied the same method to Jupiter and gained the correct value for its rotation period. According to new estimates, the period of rotation of Saturn is 10 hours 32 minutes 45 ± 46 seconds. You can, of course, ask: why do you need to know with such an accuracy the period of rotation of Saturn? Is the difference in a few minutes so important? But the trouble is that with the unknown period of the axial rotation of Saturn, it is impossible to measure the speed of the wind in its atmosphere and, accordingly, it is impossible to accurately assess the energy of the processes occurring in the atmosphere.