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From Lira San to the Kessel Run: Star Wars and Relativity


The Solo film is approaching fast, with our first canonical look at the Kessel Run that made the Millennium Falcon famous. We have multiple confirmations now that the Kessel Run is made hard to navigate by black holes in the vicinity, among other things, and this wouldn’t be the first time the new canon has shown this kind of environment as a navigational hazard. Indeed, the heroes of Star Wars Rebels faced such phenomena in their journey through a star cluster, in the second season episode “Legends of the Lasat”.

Black holes and their surroundings are the topic of the astrophysics research I do for a living, so I’ve wanted to talk about this since before I finished writing about Concord Dawn. Because I absolutely loved this scene. Accompanied by the marvelous music of Kevin Kiner, magnificent visuals depict a maelstrom of gas and dust that swirls around a number of bright, hotter spots where the black holes whose gravity dominates the entire region might be located, but they are left unseen. Indeed, the fun thing about these objects is how small and compact they are compared to their mass: the spherical event horizon of a black hole as heavy as our entire Sun would be a bit less than six kilometers wide. When the camera in the episode is pointed sideways, away from the accreting dust, blue streams of ionized gas can be seen coming out of the biggest hot spots. Some in-falling, disintegrating objects, probably asteroids disrupted by tidal forces, complete the picture. I liked it so much that I remarked at the time how, given its description in Legends sources, this could have been a great depiction of the Maw, the black hole cluster located near the Kessel Run.

But there was more. Despite the term “black hole” appearing in concept art, Hera says “imploded star” instead. They probably changed it to make it sound more exotic, but in doing so they actually increased its accuracy! The explanation is as follows. Natural ways to end up with a cluster of black holes involve massive stars exploding as supernovae. Stars tend to form in clusters, and the heavier they are, the faster they burn their fuel and the shorter they live, so massive stars don’t get very far from each other before dying. And if some of these had more than twenty-five times the mass of the Sun, they could leave black holes behind as their cores collapse (or implode). However, the formation of those stars will also produce many more of lower masses. The ones with more than eight times the mass of the Sun will live a few million years longer and their cores will also implode, but this time creating neutron stars. You would also expect some of these in a cluster of black holes like this, and “imploded star” includes both. » Read more..

The Physics of The Last Jedi


In the concluding remarks of my previous piece about the physics of Concord Dawn, I argued that one could use science to think about how something unusual in a work of fiction might happen, and its consequences and implications, rather than just calling it a flaw that was not addressed and must be pointed out. After The Last Jedi‘s release, however, many chose this second option when faced with an element from the film’s opening sequence: bombers in space.

The argument generally goes like this: it makes no sense that Resistance bombers would attack a First Order Dreadnought by flying over it and dropping their bombs, since everything happens in space where there is no gravity, and therefore the scene was just filmed that way because that’s how bombers operate on Earth and it looks cool. Mind you, that might well be the actual reason! But since we’re thinking about physics, we could go a bit deeper than this and see where it takes us. One can’t invoke the planet’s gravity to explain bombs falling onto the Dreadnought, since the ship is not oriented with its ventral side directly facing D’Qar, although its artificial gravity seems to extend a bit beyond its topside hull (as seen when debris from explosions and destroyed TIE fighters fall towards it). There’s also artificial gravity inside the bomber, as an important plot point makes us painfully aware, and that alone could have propelled the bombs away. But it turns out that gravity was never necessary—according to TLJ’s Visual Dictionary, the bombs are launched from the bomber by electromagnetic means. » Read more..

The Scars of Concord Dawn—A Physicist Overthinks Star Wars Rebels


Star Wars art designers seem to have a tendency to carve chunks out of planets lately, be it to make them part of a massive superweapon, to create a hellish and/or exotic landscape, or to show that a place has gone through serious turmoil over the centuries. The latter of those led to the newest depiction of Concord Dawn in the Star Wars Rebels episode two weeks ago, “The Protector of Concord Dawn”, as shown in the picture above. Now, I won’t lie; it looks very cool, and makes for a beautiful and interesting background, more memorable than just what a normal planet with some moons in the darkness of space would be. But still—and Mike knew this when he tempted asked me to write this piece—I can’t put my astrophysicist’s brain aside when looking at it, and as such I can’t help but wondering: could a place like this really exist? Would a planetary body retain that shape after some unknown cataclysm blows away a big portion of it into fragments, or would everything collapse pretty soon under its own weight?

To answer this, one must first gather some basic information. For example, how big is the world in question? In the episode, the surface where the Protectors’ camp is located seems to match what we see of this bigger object from space. And if we assume that it is, we can tell that it has quite an Earth-like gravity (although lower gravity in Star Wars is typically represented like this, too), a comfortable atmosphere with clouds, landscapes that don’t seem so bad harboring what look like rivers or lakes, and an intact half that looks very much like a semisphere. Taking all that into account, I’d say this world is somewhere between the sizes of Mars and Earth (6,000 to 12,000 km in diameter). This is important because size and roundness are related when it comes to planets—If you make a list of all the objects in our solar system, you’ll see that everything with a size of 1,000 kilometers and up is round, no matter how violent its past. The biggest impact basins are no more than a few kilometers deep. Even the Earth is the result of the collision of two planet-sized objects that merged to form a bigger one, and we wouldn’t know if it wasn’t for the fact that this is how the Moon came to exist. » Read more..

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