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Physics, Astronomy & Cosmology / Re: Why do the Earth's satellites orbit longer than the Moon's?
« on: 21/03/2024 23:29:10 »
Hi.
None-the-less there are so many things up there around Saturn that some moon will have some other body that will orbit it, even if that sub-satellite isn't much bigger than a dust particle.
This article ("Can a moon have a moon?", BBC sky at night magazine), https://www.skyatnightmagazine.com/space-science/can-moon-have-moon also discusses the issue. Their main conclusion was:.......
....the moons probably don?t have a large enough gravitational field to control the motions of a smaller object and compel it into orbit. The planet would likely still be the controlling influence and create an unstable orbit. So the answer is probably no: planetary moons cannot have natural satellites.
In general, it is known that the mechanics of a gravitational 2-body system will usually result in the formation of a stable orbit of the two bodies around a common barycentre. However, the 3-body problem is much more complicated. For example, one of the bodies is often ejected or thrown out of the system over enough time. It is presumably rare for a moon to retain a sub-satellite in a stable orbit around itself.
Best Wishes.
planetary satellites do not have satellitesThere are many moons around Saturn (146 according to the NASA website today - but new bodies get identified often). Of those some were thought to be moons that were in a fairly stable orbit around other another moon - but carefull examinations seem to have shown they weren't. (Reference: https://en.wikipedia.org/wiki/Subsatellite under discussion of "possible natural instances" of sub-satellites).
None-the-less there are so many things up there around Saturn that some moon will have some other body that will orbit it, even if that sub-satellite isn't much bigger than a dust particle.
This article ("Can a moon have a moon?", BBC sky at night magazine), https://www.skyatnightmagazine.com/space-science/can-moon-have-moon also discusses the issue. Their main conclusion was:.......
....the moons probably don?t have a large enough gravitational field to control the motions of a smaller object and compel it into orbit. The planet would likely still be the controlling influence and create an unstable orbit. So the answer is probably no: planetary moons cannot have natural satellites.
In general, it is known that the mechanics of a gravitational 2-body system will usually result in the formation of a stable orbit of the two bodies around a common barycentre. However, the 3-body problem is much more complicated. For example, one of the bodies is often ejected or thrown out of the system over enough time. It is presumably rare for a moon to retain a sub-satellite in a stable orbit around itself.
Why do asteroids have satellites,Many of them stay far enough away from large sources of gravitation (like a planet) that they are effectively only two-body problems, the asteroid and its satellite.
Best Wishes.
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