Weird, Wiggly Planets Could Be a Sign of Alien Life
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Researchers have found planets can share stable “horseshoe” orbits in systems of up to 24 planets.
These systems, if stable, are incredibly rare, as gravitational effects tend to throw at least one orbit out of whack.
If one of these 24-planet systems were ever discovered, researchers say it may be ground to expect advanced alien intervention.
Some things are just impossible. Some things are possible, but improbable. And some things ride the line between the two and just perfectly hit “technically possible, but probably not without help.” Recently, researchers found an arrangement of planets around a star that (if we ever saw one in real life) would fall right on that thin line—one so improbable that spotting an example may be an indicator of advanced alien civilizations.
Now, again—we’re dealing with the extremely improbable here, so we probably won’t ever see a system like this. But probing these ideas teaches scientists a lot about the dynamics and formations of stellar systems, both of which are still very mysterious to us. Specifically, the international research team behind the recently released preprint set out to better understand systems where two or more planets share an orbit around a star.
In our solar system, we have only one planet per orbit. It’s actually, technically, part of the definition for a planet. From a NASA website:
It must orbit a star (in our cosmic neighborhood, the Sun).
It must be big enough to have enough gravity to force it into a spherical shape.
It must be big enough that its gravity cleared away any other objects of a similar size near its orbit around the Sun.
But the universe is often happy to throw wrenches in our understanding of the rules in ways that make us have to rethink them altogether (remember the Pluto debacle, anyone?). And it turns out that—according to models—planets sharing the same stable orbit around a star is a possible, if not probable, situation.
The rarity is likely due to the fact that having two bodies in the same orbit begins to introduce some thorny gravitational complications. Two objects of similar sizes (like planets) can throw the other off course entirely if they interact the right way, which can result in one planet changing orbit or even being thrown from the system entirely.
But planet-on-planet perturbations, according to the models used in the study, are not always omens of the system’s doom. The paper lays out two possible ways that a stable system with shared-orbit planets could be achieved. One is that the planets are evenly spaced around the star, meaning that their gravitational interactions with each other are relatively ineffectual.
The other is more interesting, and less easy to accomplish. The researchers call it a “horseshoe” configuration, and it’s when the gravitational interactions between two planets sharing an orbit cause the planets to speed up and slow down in relation to each other as they orbit their host star.
We’ve only seen this behavior once before, with two moons of Saturn. But according to the paper, these systems are theoretically possible with up to 24 planets. A system that complex, however, is SO improbable that the researchers believe seeing one could be grounds for suspecting that an advanced alien civilization put the system into motion themselves. According to a New Scientist article, astronomer and lead author of the study Sean Raymond said that the arrangement is “either a super-duper rare outcome of planet formation, or some civilization has put the planets in that place on purpose.”
When an astronomer is saying alien intervention is more likely than a natural occurrence, it means we’re probably not going to see a system like this any time soon. But so much is possible in the vastness in the universe that it probably pays to keep our eyes open—even on an incredibly long shot.
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