The Science (& Fiction) of Star Wars: Part 1

by Sam Atkins

Happy Star Wars Day! In the spirit of May the 4th, here’s a couple of fun little things about the Star Wars universe and how they relate to real astronomical concepts.

NOTE: Tap or hover over images for captions and credits.

Twin Suns on Tatooine

Image credit: Disney

In Star Wars, Luke Skywalker lived his youth on the desert planet of Tatooine. In a very iconic but somber scene, Luke longingly looks out at the striking view of two setting suns as he dreams of a life beyond his humble moisture farm. Seeing two suns definitely gives Tatooine the feel of an alien world in a far, far away galaxy. But in the real cosmos, binary star systems are quite common. Stellar surveys of our local region of the Milky Way suggest that at least half of the stars around us have one or more gravitationally-bound companion stars. Exoplanets orbiting binary stars are also quite common. About half of all exoplanets we’ve discovered have more than one parent star.

So can a planet really have twin suns? We know they can. Can it be habitable? Well… maybe?

This is all theoretical as we only know of life existing on one planet orbiting a single star. The most crucial thing would be whether the planet has a stable orbit within the habitable zone. Where this zone lies depends on the masses, sizes and separation between the two stars which can vary quite a bit from system to system. If the stars are sufficiently distant, a planet could orbit one or the other. If the stars are sufficiently close, a planet might be able to orbit them both as a pair. While the former is much more probably, Tatooine is the latter: twin Sun-like stars of similar size orbit closely around a common center of gravity with Tatooine orbiting around them both. This is known as a circumbinary orbit and we have discovered real exoplanets with this configuration, though they’ve all been gas giants. The first of these was Kepler-16b.

Life would have many challenges to overcome on a circumbinary planet. The ever-changing distance of the two stars as they circle each other could cause significant fluctuations in the amount of light and heat received by the planet. This can make the climate too unstable for lifeforms to adapt. Wavering tidal forces could induce internal heating of the planet which could help maintain habitability but too much could cause catastrophic volcanic eruptions and earthquakes.

However, as a character in another great science fiction movie once said, “life finds a way.”

Flying Through an Asteroid Field

Image credit: Disney

There is a common misconception about how dense the asteroid belt is, largely originating from science fiction. In Star Wars Episode V: The Empire Strikes Back, there is a scene where Han Solo is navigating the Millenium Falcon through a very crowded asteroid field with the Empire in hot pursuit. As the Corellian freighter bobs and weaves between clusters of rocks, C-3PO begs him caution, saying “Sir, the possibility of successfully navigating an asteroid field is approximately 3,720 to one.”

While there is no doubt an incredible amount of asteroids that populate the asteroid belt and while it makes for an exciting and visually-appealing chase sequence, this is not reality. If you were to enter into a real asteroid field, you probably wouldn’t even see any asteroids. In fact, you could probably sleep your way through one without too much worry. The thing is that space is really, really big. The asteroid belt lies roughly between 2 and 4 AU (between 300 and 600 million km) from the Sun. That means that the outer edge has a circumference of about 3.75 billion km. The average distance between individual asteroids in the main asteroid belt is about 1 million km (600,000 mi). Yeah, you read that right.

However, I’m willing to let some creative liberties go for a fun action scene!

Dogfighting in Space

Image credit: Disney

A lot of the ‘wars’ in Star Wars is meant as an allegory for World War II. X-Wings have dogfights with TIE fighters much the same way that American P-51 Mustangs had dogfights with German Focke Wulf 190’s. These sequences, even today, are incredible to watch and the special effects hold up really well for movies that are older than I am. However, the way dogfighting would go down in the real vacuum of space would be quite different. In the movies, X-Wings are seen banking when they turn, meaning they roll their ship sideways so that the top faces in the direction they want to move.

The reason planes do this in real life is because of how wings work in Earth’s atmosphere. The wing of a plane is designed to make air pass overtop of it faster than underneath it. Faster air has lower air pressure. If the air pressure below the wing is higher, it will lift the airplane wing upward to find equilibrium. When a plane wants to turn right, it banks to the right so that that the upward lift from the air pressure is oriented right instead of up. However, in the vacuum of space, there is no air pressure to lift your wing upward or to slow you down without fuel. As Newton’s third law states, there needs to be some kind of opposing force to create or counteract any movement, whether it be to turn or slow down.

What starfighters in space would need instead of wings are thrusters that can fire in every direction. This of course makes movement more complicated and requires a lot more fuel but it also opens up a lot of possibilities that atmospheric flying can’t. For example, while flying in space, craft would be able to turn their craft up, down, sideways or even backwards without changing their original direction of movement! They can potentially fire weapons in any direction without losing momentum.

Wings on an X-Wing are not completely baseless, though, as these craft are supposed to be able to operate in atmospheric conditions as well as in space so they would likely require both modes of flight. However, they would need to be redesigned more aerodynamically (and with an actual tail) for atmospheric flight to not end in flames.