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Planets revolving around the Sun

Hypothetical case:

What could have been or no impact if the planets viz Earth, Jupiter, Saturn, Mercury, Venus, Mars, Pluto, Uranus, Neptune in different orbits revolve around the Sun in counter clockwise or anticlockwise direction?

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    $\begingroup$ I think you want to say "retrograde" (clockwise/counterclockwise depends on which direction you're viewing from). $\endgroup$
    – Sten
    Commented Jun 26, 2023 at 16:33
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    $\begingroup$ All the planets orbit the Sun in the same direction. $\endgroup$
    – PM 2Ring
    Commented Jun 26, 2023 at 16:49
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    $\begingroup$ I don't understand what the question is. Are you asking what would happen to the rest of the Solar Systerm if one of the planets orbited in the opposite direction to the others? $\endgroup$
    – ProfRob
    Commented Jun 26, 2023 at 17:15

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The direction in which planets are supposed to orbit their host star is prograde -- i.e., coincides with the direction of rotation of the star. The reason for this is that the said motions are pre-defined by the direction of rotation of the nebula that gave birth to the stellar system.

This said, it is not impossible (at least in principle) that the stellar system captures an alien object flying by, and makes it another planet. Possibly, on a retrograde orbit.

The probability of this event is extremely low, because a typical fly-by velocity is high (kilometers to dozens of kilometers per second). It is therefore not apparently obvious how the captured body would get rid of the redundant energy. A temporary capture is possible, though, -- a known fact from the theory of three-body problem.

Suppose for the sake of argument that a temporary capture happened in the early aeons when the remnants of the disk were still around, so that they helped the newcomer to dissipate enough energy to stay permanently. Also, suppose that its orbit is retrograde. Sadly, the fate of such a system cannot be predicted without numerical modeling. The system may, e.g. turn out to be chaotic -- but then, again, it is impossible to estimate the Lyapunov time without numerics.

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    $\begingroup$ Retrograde planets are seen around many stars. They are not captured objects. $\endgroup$
    – ProfRob
    Commented Jun 27, 2023 at 7:37
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    $\begingroup$ @ProfRob Why do you think that they are not captured? Can they be formed in the disk? Have such processes been modelled? I shall be glad to amend my answer if you offer more information. $\endgroup$ Commented Jun 27, 2023 at 13:29
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    $\begingroup$ What's your capture mechanism for a hot Jupiter on say a 5-day orbit? The mechanisms to produce retrograde planets are interactions within the system and with third bodies - e.g. Kozai-Lidov effects. $\endgroup$
    – ProfRob
    Commented Jun 27, 2023 at 13:33
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    $\begingroup$ @ProfRob People have modelled flips of orbits of small bodies, due to close planetary encounters. ui.adsabs.harvard.edu/abs/2022A%26A...667A..91V/abstract Will this mechanism apply to planets themselves? Has anyone modelled a planet orbit flip due to Lidov-Kozai? $\endgroup$ Commented Jun 27, 2023 at 13:40
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    $\begingroup$ @ProfRob I would sooner rely on chaos-assisted capture ui.adsabs.harvard.edu/abs/2004MNRAS.354..971A/abstract , but I certainly may be wrong. $\endgroup$ Commented Jun 27, 2023 at 13:44

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