Star Wars and the Science of Multi-Star Systems

by Caroline Binley

Come December 18, “Star Wars” will be back. Some of us will cosplay. Some will cringe. A good few might even cry, though I can’t predict whether those tears will be of joy or disgust. And all of us will look with newfound hope at Luke’s home planet, Tatooine.

Its iconic double-sunset was once seen as leaning on the fiction part of science fiction. There was no proof that it couldn’t happen, but history.nasa.gov explains that many questioned whether multi-star systems were stable enough to produce planets.

However, views on the likelihood of Tatooine-esque scenarios have changed in recent years. In 2012, the Zooniverse project Planet Hunters discovered a situation even more complex than Tatooine’s, the first planet in a quadruple-star system (PH1/Kepler-64B), with the help of the light curve pictured below.

ph1lightcurve

Light curves are graphs that measure the amount of light a telescope receives from stars over time. For more info on light curves, head over to my last post.

This specific light curve, used by scientists Kian Jek and Robert Gagliano, shows a few things.

First, you have your good old planetary transit. This is the dip created when the planet passes in front of one of the stars.

Second, you have your eclipses. The primary eclipse occurs when the dimmer star passes in front of the brighter one, blocking its light. You can see this is when the light curve dips the most, displaying only a fraction of the stars’ normal light. The secondary eclipse is the opposite, occurring when the brighter star blocks light from the dimmer one. The dips here aren’t much different than the planetary transit, so scientists didn’t originally think the binary system contained any planets.

So if you’ve been paying attention, this might raise a question: I’ve only talked about two stars, but I did say this is a quadruple-star system, right? PH1 orbits a set of binary stars (two nearby stars orbiting their common center of mass) while another binary set orbits in the distance. Scientists noticed this second set of stars when they started to gather pictures of the whole system, Kepler-64, pictured left.

According to astronomy.com, finding planets in multi-star systems isn’t surprising. Those systems outnumber single-star systems like our own. Most of them are gas giants like PH1, and they aren’t suitable for life as we know it, but new mathematical models are showing that Earth-like planets can form in these systems.

As said by the authors of Planet Formation Around Binary Stars: Tatooine Made Easy, “The circumbinary environment is friendly to planet formation, and we expect that many Earth-like ‘Tatooines’ will join the growing census of circumbinary planets.”

All this science serves to back up one point — the most important point that could possibly be made: Tatooine-esque planets are a real possibility in this universe. Which means, of course, “Star Wars” is not sci-fi as much as a very well concealed documentary on the wonders of alien life .

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