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Mystery is the behavior of the satellite of Saturn.
Astronomers found that Titan, a moon of Saturn, is gradually removed from the gas giant at a speed which is a hundred times more than expected. This indicates that the celestial body was initially much closer to the planet and had migrated to a distance of 1.2 million kilometers in about 4.5 billion years. Article researchers, which describes a previously unknown phenomenon in the Solar system, published in the journal Nature Astronomy (translation lenta.ru).
According to standard models, the Titan should migrate with a speed of 0.1 cm per year. This movement is caused by an effect called tidal acceleration. The gravitational field of the satellite generates a tidal wave on Saturn, which is due to the rotation of the planet around its axis is displaced forward in the direction of rotation. Offset mass of the gas giant “pulls” the satellite, accelerating it and causing an enlargement of the orbit. Scientists believed that this effect for Saturn and Titan is much weaker than for Earth and the moon, because the gas envelope of giant planets and its low density.
In the new study, the astronomers analyzed astrometric and radiometric data collected by the Cassini space probe. Was measured by the change in the position of Titan on a starry background, and estimated the force acting on the probe from the gravitational field of the satellite. Derived in both cases, the new rates of speed of migration of the moon of Saturn coincide with each other.
The high rate of change of the orbit is explained by the theory of resonance capture (resonance locking) proposed in 2016. Titan makes Saturn to oscillate with a certain frequency, causing the resonant increase in the amplitude of the oscillations. The result is a gas giant scatters more energy and causes the Titanium to be removed with greater speed from the planet. A similar phenomenon may occur in other systems with two stars or large exoplanets.