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I'm looking to not tidally lock my planet, but place it between two suns that rotate around each other. The goal is to have constant sunlight on all sides of the planet and for the suns to rotate at a constant speed relative to the planet. I want to clarify, I don't want the planet to relocate within the system at all.

It should rotate with the same side of the planet always facing the same side of the sun, with equal sizes binary stars. This would remove the "year", as there's no orbit to speak of, due to the lack of movement around either star.

Is this method to make a stationary planet possible?

Bonus: Could it have a livable atmosphere?

Let me know if my intent is unclear, and I'll update accordingly.

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    $\begingroup$ So the planet is at Lagrangian point L1 between the two stars. That's possible, but also unstable. Any little tiny perturbation will move it out of equilibrium. How does the planet keep station? $\endgroup$ – AlexP Jan 17 '17 at 23:19
  • $\begingroup$ @AlexP Plenty of luck? The thought is that the planet is "rotating" around both stars in opposite directions at the exact same speed, and the stars themselves are rotating at the same speed. $\endgroup$ – Anoplexian Jan 17 '17 at 23:30
  • $\begingroup$ Wrote an answer but I see after re-reading the question you are asking bout the illusion of a planet being stationary while the sun rotates around it and not that the planet stops spinning itself (meaning the planet would always have the same side to the sun). Deleted it as it is no longer relevant. $\endgroup$ – ggiaquin16 Jan 17 '17 at 23:54
  • $\begingroup$ Based on the title I was going to say "just change your reference point", but I guess that's not what you want. $\endgroup$ – JAB Jan 24 '17 at 2:41
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This is definitely possible...but very unlikely.

When you have two massive objects orbiting each other, like your stars (let's call them Alpha and Beta), there are five points where a much smaller object (such as a planet) can remain perfectly balanced.

These are called the Lagrange points, or the libration points, or just the L-points for short.

Lagrange points (via Xander89 on Wikimedia)

You're talking about using the L1 point. This is the simplest one to understand: Alpha's gravitational pull is exactly balanced by Beta's.

Unfortunately, points L1, L2, and L3 are unstable. An object can remain in place there, but it's like a pencil balanced on its point: any little push one way or the other will tip it over. A slight perturbation, a meteor strike, even a rocket launched from the planet would send it spiralling into Alpha or Beta.

So you would need some sort of correction mechanism. If this planet were constructed by the ancients using their amazing lost technology, that would be feasible; there would be some sort of engine attached to the planet that would push it back into place if it lost its balance.

But naturally, there's no way such a world would survive long enough to evolve intelligent life. There's just too much that could go wrong.

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  • $\begingroup$ The perturbation don't need to be in the planet. Perturbations to either star could also make the planet drift out of L1. Further, small gravitational disturbances that are introduced by other planets might also do so. That engine would need to be very advanced. $\endgroup$ – Victor Stafusa Jan 17 '17 at 23:57
  • $\begingroup$ @VictorStafusa Very true! L1 is good for satellites, less so for inhabited planets. $\endgroup$ – Draconis Jan 17 '17 at 23:59
  • $\begingroup$ No, the ancients would create self-replicating engines which accidentally got out of control and crushed the planet by all pushing inwards at once. $\endgroup$ – iAdjunct Jan 18 '17 at 3:37
  • $\begingroup$ Isn't L1 semi-stable if the scale of the objects is wildly different? If the two stars are particularly massive compared to the planet, I think the planet can have a very tight orbit around the L1 point and remain there even with perturbations. Yes? $\endgroup$ – SRM Jan 18 '17 at 6:47
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    $\begingroup$ @SRM Unfortunately not. You're thinking of the L4 and the L5 points, which are semi-stable if the ratio of the masses is greater than 25:1 or so. But L1 is never stable; if the planet moves any closer to Alpha, now Alpha's pull is stronger than Beta's, pulling it even closer... $\endgroup$ – Draconis Jan 18 '17 at 6:51
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To me, it sounds like you're looking for a single star with two tidally locked orbiting bodies. One of the bodies is a planet - and beyond this planet at some distance a second, tidally locked star. This is interesting, because the whole thing would kind of be spinning together in the end, though the length of this cycle would make little difference to the observers on the planet, who would only and then only possibly, barely, see stars from the meridian equators - those meridians at a 90° angle from the two stars.

Considering that from some reference frame there is always going to be some motion, your world might be best explained this way. while on the surface of the planet, it might not be possible to tell the difference. The delta in size, distance and luminosity, not to mention the kinetic history of the orbiting bodies in question could add up to an improbable, but physically possible stellar and planetary system. In an infinitely large universe, every improbable arrangement of particles consistent with the laws of physics will likely obtain somewhere, right?

I'd add that an atmosphere is perfectly possible between two stars. There is concern that the tidal forces might cause intense geological processes to occur, but the amount and type of radiation as well as the phase of life of the star is what will dictate where it lies, with respect to the local "goldilocks zone" - there is no reason the star could not be totally bright, and freezing cold.

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For the livable atmosphere bonus question, you should consider that we have an atmosphere on Earth because Earth's magnetic sphere protects us from the sun's solar wind blowing it away. Your planet would be hit with solar winds from two suns, and these could be strong enough, together, to destroy the atmosphere. I doubt the winds could somehow balance each other.

But then maybe both winds are relatively weak. I don't know what that would imply about the age or strength of these suns.

Other aspects of our sun would also get doubled up, such as the amount of radiation. The ozone layer could get stripped away. A lot could go wrong to make life unlikely.

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