You seen Newx explode? You've seen planets explode? Now, you're going to talk about STARS exploding. Are you sure about that? First discovered in the year 185 AD by some random dude in China, a supernova is a massive explosion that occurs at the end stages of STARS' life cycle. They are very rare with the last supernova from our own galaxy, being witnessed in 1604 by various astronomers including Kepler. The first thing that needs to be addressed, however, is that it was between a nova and a supernova. A nova is a star that will randomly decide that it wants to be really bright for a few days, then go right back to its original brightness. Nove are usually caused by white dwarves, those things that are left behind when a low-mass star runs out of juice and dies, and are normally very dim in the night sky. In order for them to have enough energy to become a nova, however, a white dwarf must be part of a binary system, stealing matter from the larger neighboring star, and creating an accretion disk, which is just a large disk of matter surrounding the white dwarf. A supernova, on the other hand, is what happens when Michael Bay looks into the night sky. These insanely large explosions are only possible with high-mass stars like beetle juice and cannace majoris. This is because low-mass stars cannot become hot enough to burn carbon or any other heavy elements. Thus, they can only burn hydrogen and helium fuel, and when it runs out, they just turn into white dwarves. High-mass stars are different, though. High-mass stars have enough heat to burn all the way through carbon, oxygen, and pretty much every element on the way down to iron into their cores. Now I know I'm asking a lot here, but I need you to remember your time in chemistry class, particularly the periodic table. First, a star burns through its hydrogen, fusing into helium through fusion. If you need to remind of what fusion is, it's when two atoms smack into each other at really high speeds, and then get stuck together, the energy released from which is what gives the star's heat and its light nuclear explosions. The process of fusion for high-mass stars continues further on from helium, though, through carbon, then oxygen, all the way to iron. Now iron is where things get a bit interesting. Due to iron being extremely stable, fusion becomes impossible inside of a star. Its nucleus is so compact that energy cannot be extracted from it by changing it into a heavier or lighter element. Therefore, once iron shows up in a star's core, it begins permanently losing energy. At this point, everything starts happening quickly. The star's core gets hotter and hotter. If you remember, of line's law, then you'll know that at extremely high temperatures, individual photons possess ridiculously high amounts of energy. In this case, enough to split iron's really compact nucleus into lighter elements. And then split those lighter elements into even lighter elements. And then those even lighter elements into individual protons, neutrons, and electrons. This process is called photo disintegration, and it's not a fun process for the star. Through photo disintegration, the core goes through all of its materials in a matter of seconds. However, splitting all of these elements requires immense amounts of energy, too much for the star to provide. That means that during this process, the star throws all of its energy into fission, which cools the core and reduces the pressure inside. Now, there is nothing left but electrons, neutrons, protons, and photons. All packed together at extremely high density. As the star starts shrinking and the density increases, photons and electrons are actually crushed together to form neutrons and a really compact little particle called a neutrino, which sort of exists, but also sort of doesn't. But that's some high concept stuff that isn't really important to us right now. So, ignore it for now. Now, the electrons have been merged with the protons, and the neutrinos had said, screw you guys on going home and have escaped into space, leaving nothing to self-the-star from saying screw it and collapsing all the way. Once the star gets to this point, however, the neutrons continue resisting each other as they get closer and closer due to gravity, producing intense pressures that slow the core's collapse. However, by then, it's already too late. The core is no longer in equilibrium and may increase this density greatly before, once again, expanding. Now, before we get to the good bit, let me just summarize what just went down, because it's a bit complicated. In a nutshell, core mix iron, iron causes the core to start shrinking, and now it shrunk so much that it's about to expand again. You get? No? Well, too bad. So, I'm going to simplify a lot of science, jargon. The star goes boom. Now, you may be asking yourself, how big is this boom? Well, here's a picture of the aftermath of a supernova that we saw a while ago in another galaxy. There are also multiple types of supernova that can be categorized in Type 1 and Type 2. For Type 1 supernova, it will suddenly get very bright, then dim in a mostly linear fashion. Type 2's on the other hand will get very bright, start dimming, but then plateau for a bit before dimming all the way. Type 2's can only occur with high mass stars, because those are the ones that go bang. Also, Type 1's have very little hydrogen, according to their spectra, whereas Type 2's have very large amounts of hydrogen. Okay, okay, okay. Now, I know you're going to hate me for this, but I've got some bad news. There are more ways for a supernova to detonate. The supernova I just described is called a core collapse supernova, where you guessed it, the core collapses on itself. There is also the carbon detonation supernova. Now, to explain the carbon detonation supernova, we need to go back to white dwarves. I'm just going to make this very simple and say that a white dwarf in a binary system steals enough mass from its neighboring star, then the core of the white dwarf immediately just collapses on itself, due to the increases of mass. Carbon diffusion begins throughout the entire white dwarf at the exact same time and then blows up. So, it's not so much an explosion as an implosion, and a violent one of that. This is what causes a Type 1 supernova, the one with very little hydrogen. So, what's left after a supernova? While in most cases, nebula are what remains. These large clouds of gas and dust are all of the elements that were once inside of the star that just pulled a chowtsu and detonated themselves. One of the most famous of these nebulas, the Krab Nebula, is actually the remnant of a star that detonated itself during the Middle Ages, and is still around today and has been studied ever since. The explosion also leads behind heavy elements. I'm going to summarize six pages of textbook here, and just tell you that after the explosion, the atoms smack into each other and make the rest of the periodic table. The key in turn is going to need to know here are stellar nucleosynthesis, helium capture, and neutron capture. Wait, but if stars keep exploding, how do we still have new stars being created? Well, if you remember from what I'm assuming the other groups told you, stars are created inside nebula. Where do nebulas come from? Dying stars. Basically, a star is made in nebula, it goes through its life cycle, then assuming as a high mass star, or a low mass star in a binary system, it goes supernova, creating heavy elements that are spread out in a new nebula, and the dust from that new nebula is used to make new stars and planets. The term for this is stellar recycling. Through this, the universe keeps on trucking, even as his stars keep on detonating. Ain't that right, Michael Bay? I can feel the tumors growing on my back.