In our Solar system all objects at least and take up some certain places, in fact, are in constant motion – the planets away from the Sun, and their satellites are in a hurry to fly away from the planets. The speed of the escape small and is measured in centimeters per year, but recently scientists have found that previous data for Titan, moon of Saturn, was fundamentally incorrect. He moves away from his planet at least 100 times faster than previously thought.
The reason for the escape is the tidal acceleration, which is due to tidal friction – the mutual influence of gravity of cosmic bodies in their substance. On Earth it is expressed in the form of the tides of the oceans depending on the phases of the moon. The earth also affects the moon, giving it an extra orbital acceleration. So the Moon moves away from our planet with a velocity of 3.82 cm per year. Since Saturn is made of gas, scientists believed that a similar process occurs there more slowly – by about 0.1 cm per year.
Using data from the Cassini spacecraft, scientists have conducted astrometric measurement of the position of Titan relative to the stars. Comparison with similar information of previous years has shown that the actual removal rate of the satellite of about 11 cm per year. The researchers then took the radiometry using data such as that of Cassini, and calculated changes in velocity of the satellite under gravity of the planet itself. The results of the astrometry and radiometry coincided perfectly (which in itself is amazing).
It remains to understand why the rate of removal of Titan from Saturn is so great. A working hypothesis is called “resonance coupling”, this phenomenon occurs in the confrontation of double stars. They affect each other gravitationally and the smaller of the two bodies gets greater impetus, and that is the reason for his repulsion. To test the hypothesis, we need similar data for other satellites of Saturn, which are still being processed.
Source — Nature Astronomy