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.
SPOILER WARNING: This article contains spoilers for Star Wars (1977) and Star Wars Episode V: The Empire Strikes Back (1980), but you should take this as a general spoiler warning for the Star Wars franchise.
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 probable, 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 1.”
There is no doubt an incredible number of asteroids that populate the main asteroid belt. There are over 1 million asteroids that are at least 1 km across, but more recent surveys suggest it may be double. However, if you were to enter into the real main asteroid belt, you probably wouldn’t even see any asteroids at all.
The thing is that space is really, really big. The asteroid belt is a vast torus that orbits around the Sun between the orbits of Mars and Jupiter. It has an elevated concentration of asteroids compared to other regions, but it is still almost completely empty space. The radial thickness of the asteroid belt is about 150 million km from the inner edge to outer edge. That’s about the distance between the Earth and Sun. The average distance between individual asteroids in the main asteroid belt is about 1 million km (600,000 mi). That’s nearly three times the distance between the Earth and the Moon! Things are starting to feel a lot roomier. The Expanse series gets this right. Much of the show takes place in and around the main asteroid belt, yet spacecraft are regularly shown surrounded by nothing but empty space.
A small caveat: You may have caught that the previously stated 1 million asteroids in the main belt are 1 km and you’re probably wondering about all the smaller asteroids. It is very true that these smaller asteroids would far outnumber the bigger ones, likely in the hundreds of millions range but we just can’t see them from Earth. However, even when factoring these in, we are still talking distances between individual asteroids in the 100,000-300,000 km range. For comparison, Saturn’s ring system spans about 280,000 km across.
All things considered, the asteroid chase sequence in Empire Strikes Back is still an exciting, visual feast and I’m more than 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.
All that being said, there’s very good reason to think dogfighting in space wouldn’t really be a thing in actual space-based warfare. In WWII dogfights, airplanes often fought within visual range because radars were still very imprecise, the atmospheric and nighttime conditions limit visibility range and weaponry was unguided. Conversely, futuristic spacecraft would likely be able to detect one another from vast distances in the emptiness of space, where there is little to hide behind and few ways to approach unnoticed. Also, the aforementioned omni-directional thrusters while more realistic than wings, would still be incredibly draining on the limited fuel reserves of smaller fighter craft.
For all these reasons, a space battle would less resemble the fast bobbing and weaving of close-range fighters and more the methodical long-range positioning and standoffs of submarines, except the ocean is completely transparent. Momentum punishes sharp turns, making evasive maneuvers limited and strategic. Thus, the advantage would go to whoever found who first, without be found themselves. Sensors, deception, heat signature reduction, and electronic warfare would replace flashy barrel rolls and speed. Devastating hypervelocity weapons would be fired from thousands to millions of kilometers away. In a real space fight, if you are trying to physically dodge enemy fire, you’ve already lost.