There’s been a lot of talk in the news lately about the star Betelgeuse, and whether it’s about to explode and go nova. The main reason this discussion is happening is because the star suddenly got very dim very quickly, and dimmer than we have ever observed it to be. The dimming itself isn’t unusual because Betelgeuse is a variable star, meaning that its apparent brightness changes. What’s unusual now is the magnitude of that change. In only two months, Betelgeuse dropped from 10th brightest star in the northern night sky to 21st.
Stars and the physics in them have always fascinated me because they are a perfect example of macro and micro coming together — the very large displaying the power of the very tiny at work.
Fusion without confusion
What is a star? Simply put, it’s a big ball of gas that is so massive that its own gravity makes it ignite in nuclear fusion, creating heat and light. As far as we know, the very first stars started out as cloud of the lightest, simplest element, hydrogen, which in its basic form is one proton with one electron bound to it. I say “bound to” rather than “orbiting” because that old model of discrete little electrons circling the nucleus like planets orbit the Sun is just wrong. It’s better to think of the electron or electrons as existing as a potential force spread out over a certain area statistically, with the shapes and volumes of those areas varying with the energy of the electron. It’s not in one place at any given time, but it’s likely to be in certain places and not in others, and this goes for every electron in the atom.
Yes, welcome to the weirdness of quantum physics. The layman’s takeaway here is that the electrons create what you can think of as a force field far “above” the nucleus that keeps other nuclei from getting too close. They’re like the walls of houses that keep the nosy neighbors from wandering in.
And that works just fine on most scales. The electrons are doing all of the work so that the atoms in your cells don’t fuse together and it even works right up to the level you can perceive. When you touch a table, for example, you aren’t really touching it. Rather, the electrons in your finger are bumping against the electrons in the table and are acting as mutual bouncers keeping each other out so that your hand and the table don’t merge.
Oh, sure, you will exchange some electrons with whatever you touch because they can just be finicky like that. But, for the most part, this is an impenetrable barrier that keeps things well-defined.
It doesn’t break down until enormous forces come into play. In the case of stars, that force is called gravity, and it’s not until that ball of hydrogen reaches a certain density that things begin to happen. Mainly, the force of gravity working on it becomes enough to overcome the force of the electrons maintaining boundaries. All of a sudden, those neat electron orbital shells go wonky, and the protons start to get to know each other. Now, normally, they would repel because they have the same charge, but their charges are so much weaker that by this point it doesn’t matter. Protons start to get forced together, and then the magic happens.
I won’t get too heavy into the physics here — you can learn more if you’d like — but the key point is that this gravitational mushing turns hydrogen into helium, the next heaviest element, which has two protons, two neutrons, and two electrons, and in the process a lot of energy (relatively speaking) gets released.
This continues on for a long time until the hydrogen has almost but not quite run out, at which point the star starts to smoosh all of that helium into carbon, and the process cascades from there. Combining each new element with more helium runs down the chain to create oxygen, neon, magnesium, silicon, sulfur, argon, calcium, titanium, chromium, and then iron.
A star is basically a forge that creates the heavier elements that become the building blocks of planets, all subsequent new stars (which don’t start as pure hydrogen), and, eventually, life.
There’s one critical element to mention, though: while the force of gravity has been enough to make the fusion happen, at the same time the opposing force of the energy released by that fusion has been enough to push back and create a sort of equilibrium so that the star doesn’t collapse or expand. It pretty much maintains its size.
And then iron synthesis comes along, and it’s a game changer. Why? Because, unlike those other fusion reactions, this one doesn’t produce sufficient energy to fight gravity any longer. Boom, it’s like a light switch is turned off. All of a sudden, the floorboards give out, and all of that mass up above the ceiling is free to come crashing down into the basement, and that doesn’t go well when it hits bottom. Above a certain original mass, you get a black hole. Below it, you get an enormous explosion which scatters all of those elements outward and releases an incredible amount of energy.
It would be a super nova
If that happened to Betelgeuse during 14th or 15th centuries, we’d see it here soon, since the star is only about six hundred light years away. For a while, it would be brighter than the full Moon at night, and visible during the day. And it couldn’t happen to a nicer star. It’s one that you’ve probably seen since its constellation is so memorable.
Betelgeuse is the right shoulder of Orion, assuming that he’s facing us, and is visibly red from down here. In official terms, the star is known as Alpha Orionis, meaning the first, or brightest, star in the constellation Orion. The interesting part about this designation is that it’s only sometimes the brightest, again because of the variable thing. Rigel is often brighter, but when Sir John Herschel made his observations and his catalog, Betelgeuse was brighter, so it got the A rating.
If you’re wondering about the name of the star, it’s got nothing to do with the Tim Burton film. Rather, it comes from the Arabic name for it, إبط الجوزاء (‘iibt aljawaza’). If you pronounce it fast enough a few times, it kind of starts to sound like “Betelgeuse.”
Just don’t say it three times. Or, maybe, do — because seeing a supernova of this magnitude at this point in our history wouldn’t only be great for humanity in general, it would be a boon to many different sciences. The last visible supernova happened in 1987, but it was only visible from the Southern Hemisphere, and it was about 160,000 light years away, or just over 49,000 parsecs.
This one would be visible by everyone in the Northern Hemisphere, day and night, for a good period of time, and it would serve to make people aware of the universe out there, and maybe even ask questions and listen to scientists. It might even get them to realize that the ultimate survival route for the entire human race — and a lot of other species on this planet — is to get off of this planet and start colonizing, except to do it in a low-impact and benevolent way, rather than the slash-and-burn methods used by our ancestors who raped and pillaged their way out of Europe and into the “new” world. (Funny how none of it was new to the people who had been living there already.)
Anyway… here’s to hoping that one of the most violent events in the universe can grace our night and day skies soon, and pull us out of ourselves. Maybe we do need a cataclysmic event to unite the planet — but that doesn’t mean that the cataclysm needs to be anywhere near us. Just that we need to be aware of it.
What better screen than the sky above?
If you say the name three times, it appears. Betelgeuse.