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UmbralRaptor t1_iwt9d4w wrote

No, for a few different reasons.

A planet that's tidally locked cannot have a planet/moon in a stationary orbit, because that orbit would lie outside the planet's [sphere of influence](https://en.wikipedia.org/wiki/Sphere_of_influence_(astrodynamics)).

An alternative reading of the question could be having body B at the L2 Lagrange point, though that's an unstable orbit, and the body would no longer be perfectly aligned in very short order (and out from the L2 point entirely fairly quickly).

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bstabens t1_iwtfxvf wrote

In a scenario where planet B is perpetually in planet A's shadow, wouldn't that mean both planets are in a tidally locked orbit around the sun and not the one around the other?

As in, yes, that scenario is possible, but not with the requirements you want?

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Lyrle t1_iwuprni wrote

No, not possible. Orbital speed is a function of distance between the two bodies, with closer orbits having faster speeds. This compounds with closer orbits also being shorter paths. The lit planet would be going around its star faster than the eclipsed planet, which would then un-eclipse it.

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[deleted] t1_iwth262 wrote

[removed]

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bstabens t1_iwtmeig wrote

Ehm, no, and you are right - having the same side to the sun always doesn't amount to nothing.

No, I was thinking more like two planets, close orbits, the outer slightly faster so it never really leaves the shadow of the inner. But I guess it is physically not possible to have a (two?) stable orbits of two big masses so close together that you'd see the shadow? I mean, even with the moon earth's shadow is so blurred the moon never gets black, just red.

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HomeAl0ne t1_iwtoy4h wrote

The one further out would actually orbit slightly slower and fall behind.

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bstabens t1_iwtta6e wrote

As in that's a physical law? Or just we don't have examples to the contrary?

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Cmagik t1_iwtucqy wrote

Physical law The further away you are the slower you rotate around the object.

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bstabens t1_iwtucz2 wrote

Scratch that, just thought about it. Of course the dust disk where the planets come from would be slower on the outskirts and fastest at the center.

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brasticstack t1_iww4uvn wrote

More like those funnel things that you can send coins down when you're at the museum.

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Ok-disaster2022 t1_iwv4iuy wrote

Arguably couldnt B be considered a stalleote of A that has an orbital period of once a year?

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NorthernerWuwu t1_iwyl868 wrote

Well, in a three body system at least. One could design a four body (or more) system such that the gravitational centre, the orbiting tidally-locked body and a gravitationally bound body orbiting the tidally-locked body were all static, given the influence of another body very specifically placed to keep the 'orbiting' one in the shadow perpetually.

Without crunching the math though, it would be a terribly weird system and likely with the orbiting body being very far from it's parent and essentially hovering between orbiting the solar mass and its planet. That and requiring a massive object in a leading orbit at a significant distance from the planet in question.

The whole thing would be jittery as hell but plausible in a spherical cow sort of way. (In retrospection, it might well require a series of increasingly massive bodies in increasingly interesting orbits. I still maintain it is plausible in a purely theoretical way but in no way feasible to occur through nature or design.)

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didntpayforshit t1_iwvg1ch wrote

Doesn't the jwst balance itself on the l2?

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