Tatooine and the Three-Body Problem

I recently ran across a blog post that pointed out that Tatooine (the Star Wars planet of double-sunset fame) could never exist because of the problems inherent to the 3-body problem. Specifically, Kepler’s laws of planetary motion get all wonky when you are dealing with more than the two bodies: the planet and the sun. In fact, orbital patterns can start to look a little crazy, and yes, in situations like that, Tatooine would not survive long enough to even form, let alone be settled by sand people, Jedi, and various assorted scum and villainy.


Except that this doesn’t have to be the case. There are a variety of cases where a planetary orbit can be quite stable in a binary star system, provided it’s in the right place.


Yeah, that’s right, it’s all about orbital real estate. The sweet spots seem to be either very close to one of them, or very far away from both.

orbit_1star_stable1When the planet is much closer to one star than the other, the distant star does not have much gravitational influence on the planet’s orbit. It can orbit the smaller star in a nice circular orbit, almost as though the other star weren’t there at all. Well, it looks like a circular orbit from the point of view of the nearby star. From the point of view of the system’s center of gravity, it’s more akin to a spirograph. (And yes, I know that this dates me, but spirographs were cool!)

orbit_1star_stable2Here, instead of Tatooine’s double-sunset, you’ll have half the year with no night at all. Sure, one sun will set, just as the other one is coming up. I imagine that will be summer, regardless of the planet’s tilt, because overnight lows only come when there is night. It might make for an interesting place to live, but the seasons could be a little intense.

A more Earthlike (or at least Tatooine-like) experience will come if you can get far away from both stars. Put them together in the center of the system, spinning merrily around each other, and stay out in the suburbs where it’s cool and relatively steady.

orbit_2star_stable2Here, your orbit is stable, close to circular, and any seasons you have will be due to axial tilt, not varying proximity to the great fiery balls in the sky. Plus, you know… the infamous double-sunset.

But this isn’t just me jerking around with a gravity simulator. Nope, it’s backed up by actual observations. Now that we have a decade’s worth of observations from the Kepler satellite telescope, we have actually found a number of planets orbiting in binary systems.  So far, we have found at least five planets orbiting tight binaries, much like Tatooine.

So, don’t throw away your Star Wars travel plans. Tatooine is very likely out there somewhere, possibly in a galaxy very nearby.