The giant planets of the solar system surround entire systems of dozens of natural satellites. But rocky planets have very few of them: two, like Mars, one, like Earth, or none at all, like Venus.
Only occasionally does our planet capture asteroids passing by, which become its temporary satellites – not too massive and short-lived.
It is estimated that, on average, they manage to complete about three revolutions around the Earth and fly away in less than a year.
This led scientists to the question of how many satellites the Earth could potentially hold without significant changes in orbital characteristics.
“In previous work, I studied the “packaging” of the Alpha Centauri binary system. Then we learned to estimate the number of planets that could stably exist in the habitable zone of a star, explains Professor Billy Quarles, one of the authors of the new work.
“Now my colleagues have set the boundaries for the Earth’s satellites, which allows us to use the same dynamic formulas.”
Calculations have shown that our planet could hold a different number of satellites, depending on their mass. With sizes comparable to the Moon (3500 kilometers) – up to four, with Pluto (2400 kilometers) – five, with the dwarf planet Ceres (950 kilometers) – up to eight pieces.
It may be recalled that the relatively dense “packing” of the moons of planets such as Jupiter and Saturn creates unusual effects.
In particular, under the action of tidal forces that arise when moving in the gravitational field of the planet and neighboring satellites, the bodies heat up, which causes, for example, active volcanism on Io.
According to the calculations of Quarles and his colleagues, this could hardly have happened near the Earth, even if its satellites were more numerous: this would have been prevented by the gravity of the relatively close Sun.
The authors hope that their work will help in the search for satellites around distant terrestrial exoplanets. So far, scientists know of only a couple of such candidates, and both of them ( Kepler-1625b-i and Kepler-1708b-i ) orbit gas giants like Jupiter.
But if satellites can be quite numerous and small rocky planets, the chances of finding such bodies increase. Perhaps new calculations will help to find them.
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