Habitable planet at L4/L5 of binary gas giants?

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Discussion Overview

The discussion explores the plausibility of a terrestrial planet existing at the L4 or L5 points of a binary system of gas giants, focusing on stability, habitability, and the dynamics involved in such a configuration.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant questions the stability of a terrestrial planet at the L4 or L5 points of two gas giants, suggesting it may be ejected.
  • Another participant states that a mass ratio of approximately 25 between the two gas giants is necessary for stability at these points.
  • A participant raises the issue of the duration of stability, noting that while short-term stability may be achievable, long-term stability (e.g., billions of years) is more complex.
  • Concerns are expressed regarding the safety of a planet in 'halo' orbits around the L4 or L5 points, suggesting that it may not be secure from perturbations leading to impacts.
  • One participant speculates that a planet positioned at the trojan points may have a longer lifespan, potentially allowing for the evolution of life beyond single-celled organisms, though they express doubt about this possibility.

Areas of Agreement / Disagreement

Participants express differing views on the stability and habitability of a terrestrial planet at the L4 or L5 points, with no consensus reached on the feasibility of such a scenario over long timescales.

Contextual Notes

The discussion highlights uncertainties regarding the mass ratios required for stability, the duration of potential stability, and the dynamics of orbits around L4 and L5 points, which remain unresolved.

Malapine
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Would it be plausible to have two gas giants orbiting each other, a few million km apart, with a terrestrial planet at their mutual L4 or L5 point so that they both appear as visible disks fixed in the sky? Or would the terrestrial planet not be stable there and end up ejected?
 
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The two giants would have to have a mass ratio above approximately 25 (i.e. one of the giants has to be 25 times more massive than the other) for their L4 and L5 points to be stable (for a particle there).
 
A possibly better question is "for how long"? A year? Easy. A hundred billion? Not so easy. In between is, well, in between.
 
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Vanadium 50 said:
A possibly better question is "for how long"? A year? Easy. A hundred billion? Not so easy. In between is, well, in between.
And for a "Habitable planet" you probably need billions.
 
IIRC, even in 'halo' orbit around those nominally stable 'points', the unfortunate planet is not safe. Rather than perturbation causing ejection, it is more likely to become an impactor...

Which, IMHO, would be something to watch. By comparison, the SL_9 fragments' was almost trivial.
( FWIW, when I wondered if Jupiter's Great Red Spot was spawned by a mega-impact, it went badly... )

Ahead or behind at 'trojan' points of the two giants' combined mass-centre, your planet may stay around for a lot longer. Long enough for life to evolve beyond single-cells ??? I doubt it...
 

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