Plot speculation for Star Wars VII: The Force Awakens is reaching its peak in the weeks before the movie opens. Some suggest the First Order has a super weapon—the Starkiller. This is essentially a more powerful version of the Death Star that doesn't destroy planets, but solar systems. Perhaps the best way to destroy a solar system is to explode the central star. So, how do you kill a star with a Starkiller? Here are some possible ideas.
You are probably thinking that all the methods simply explode the star, and in a way, that's true. However, for this first method I am considering just putting enough energy into the star such that all its material is spread out. If you put an explosive inside of an apple, the apple explodes. The pieces of the apple would separate from the rest of the apple pieces and move in different directions.
There is a big difference between an apple and a star. Two forces hold an object together. For the apple, the primary interaction keeping the apple together is the electrostatic interactions between different molecules in the atoms. The star is a bit different. It is held together by the gravitational force (it's too big to keep together with other forces).
So, if you want to destroy a star you must add enough energy to essentially increase the size of the star. Decrease the density of the star to something like the 1,000 atoms per cubic centimeter and you essentially turn that star into a non-star.
How much energy would this take? I'm not sure—but it seems like I could get an estimate if I calculate the change in gravitational potential energy going from the first star to the blown up star. It shouldn't be too difficult.
A star like our sun is mostly in an equilibrium state. There is fusion in the core that makes heavier atoms at high energies. These high-energy atoms push the outer parts of the sun and essentially balance the gravitational forces that want to crush the star. So, you have fusion pushing out and gravity pulling in. Yes, it is more complicated than that, but that's the general idea.
But what would happen if the rate of fusion changed? If the rate of core fusion increases, the core pushes more on the outer parts of the star, causing it to expand. However by expanding, the pressure in the core can decrease to reduce the fusion rate. This allows the star to gravitationally collapse and rapidly increase the core pressure and fusion rate. The result is a supernova. BOOM. That's the end of that star.
Now we are left with finding a way to increase the fusion rate. That's where the Fine Structure Constant comes into the picture. If you looked at the fusion of two atoms in the core, it would depends on several factors:
- The fundamental charge of an electron/proton—we call this e.
- The speed of light—represented by c. Yes, this is important in fusion.
- Planck's Constant—h. Just trust me on this one.
- The Coulomb constant—k. This is in the electrostatic force.
You get the idea. There are many fundamental constants affecting the fusion rate in the core. Change any one of them and fusion changes. However, we can kind of represent all of these constants with just one constant—the Fine Structure Constant. You can think of it as The One Constant:
Change that one constant and you can make the star unstable and, for all intents, explode. It's just that simple. Oh, but how do you change the Fine Structure Constant? How do you change it, and change it only in that star? I have no idea. Or maybe I do but I'm afraid to let the New Order build a better starkiller.
This method is similar to the previous method. If we decrease the temperature in the core, the fusion rate would decrease. This could cause a gravitational collapse that would trigger a supernova. And how do you decrease the core temperature? Laser cooling.
Laser cooling is a real thing. It works because light can push on matter in the same way sunlight pushes on one of the tails of a comet. If you could push on atoms to make them slow down, the temperature would decrease. Seems simple, but there is a problem. The particles in the core of the sun move in all directions. How do you push on some atoms to slow them down while not pushing on other atoms to speed them up? The answer is the Doppler Effect.
The Doppler Effect says that as you move toward a source, the observed frequency of light is higher than the actual frequency of the source (this is called blue-shifted). As you move away from a source, the light appears at a lower frequency than the actual source (red-shifted).
Here is the magic part. If you pick the correct frequency of light, the two interactions (moving toward and away) interact differently. You can make it so that when the particle is moving toward the light, the light pushes on it to slow it down. When the particle is moving away from the source, the interaction is much weaker. The net effect is that particles slow down. Slower particle mean lower temperature and less fusion.
But wait! How do you get a laser into the center of the star? Wouldn't it have to go through all the stuff on the outside of the star? Yes. That's a good point. I don't have a perfect answer. What about this: There are two lasers. The first laser somehow pushes stuff (destroys it) creating a path to the core. The second laser shoots into the core to slow stuff down. These technical details should be left to the engineers.
There are questions left to be answered.
- If the starkiller kills stars, how do you kill a star without killing yourself since the resulting supernova will have a very large impact area?
- In some rumors, it appears the starkiller is built into a planet. How do you move a planet (or maybe you shouldn't—see the previous homework question).
- Let's say your starkiller is in a nearby solar system—maybe three lightyears away (but that's still too close). What kind of angular widening (not sure about the exact technical term) would your laser need in order to hit a star?
- Approximate the change in gravitational potential energy for the material in a star (assume one like our Sun) as it expands to create a density of 1000 atoms per cubic centimeter.
- Approximate the percent of hydrogen that needs to be converted to helium in order to increase the size of star in the previous question.
