Informative Speech On Supernovas

Introduction:

Have you ever heard the phrase “We are stardust”? Chances are you have, but what exactly does that mean? As an Astronomy major and someone whose always been fascinated by the wonders of space, including the wonder of supernovas. I want to pass some of the information I have learned to you today by telling you the different types of supernova and what happens during a supernova.

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Supernovas are explosions from old stars at the end of their life cycles. Their explosions are the largest and most energetic things in the Universe and can outshine their entire home galaxies. Supernovas can also provide beautiful viewing as well. Anyone in 1572, for a few weeks, could look up at the sky and see a bright “New star” in the sky.

Now, that supernova is known as the Crab Nebula and we can still see the remnants of the explosion today through telescopes, although we cannot see it in the sky any more. It’s very beautiful, and most supernovas of its kind are very similar in beauty.
1)
Supernova come in two forms, but neither in related to the other in any way. The first kind, called a Type I supernova, is a supernova that happens in a binary star system, usually with a white dwarf and a main sequence star or a red giant. The second kind, called Type II, happens from just a Red Supergiant, and happens at the very end of its life. The processes for these two different kinds of supernova are also vastly different. In a Type I supernova, the white dwarf will steal matter from its companion until it becomes too large, and with a Type II the explosion happens when the Supergiant runs out of fuel and cannot burn any more.
2)
To elaborate, Type I supernovas come from White dwarves and other companion stars that are in a system with one another.

As the White dwarf travels around the other star, if it has a strong enough gravity, it will begin pulling matter from the outer layers of the star into something called an accretion disk, not really coming into contact with the dwarf itself. This event alone does not actually cause the supernova, but over time, a series of smaller novas will occur from the White dwarf. A nova happens after the dwarf has collected some matter from the other star, and the star will shed some of that matter into space through a smaller explosion, which will cause a brightening of the star that can be detected through a telescope, but not to the human eye unless it happened much closer to Earth. But, because not all of the matter will be ejected into space, some will remain, and eventually, after hundreds or thousands of novas, the matter in the accretion disk will have built up so much that it has increased the gravity of the White dwarf. However, because white dwarves are meant to be small with a relative low gravitational field, this becomes a problem. Once enough matter forms in the accretion disk, the white dwarf will pass the Chandrasekhar Mass limit, which is basically the limit of how large a white dwarf can be, before its gravity will fold in on itself, which is exactly what happens after the series of novas. Once it passes the Chandrasekhar limit, because the

gravity is much stronger than what a white dwarf can handle, it will collapse, causing all the particles to come together and become denser and hotter. This will cause carbon to form, and because it’s a heavier element, it will make the gravity stronger and pressure weaker, and the star will collapse even more. Once it reaches an incredibly dense point, the star will quickly expand and explode into space, in the process creating heavy elements and becoming hotter still.
Back to the beginning again, this time with Type II.

This type of supernova begins at the end of the life cycle of a star. The star will need to have a mass greater than the sun’s mass. This extra mass will allow for more fuel and the ability to become a supergiant. Throughout the star’s life it will burn up all of its hydrogen in the core, and once it reaches that point, it will begin to fuse heavier elements such as neon and magnesium. These processes are not good for the aging star, because as it does this it becomes harder and harder to produce even heavier elements. By the time it gets to iron, it becomes impossible to create any heavier elements. Also, because it’s been making heavy elements, the star has become heavier itself, creating a stronger gravity. But, the pressure hasn’t changed, so the heavy star collapses in order to find a new equilibrium. However, as it collapses, the temperature becomes hotter and more elements form. The star becomes hot and dense to a point where even atoms begin separating, creating separate protons and neutrons. This separation causes a decrease in pressure, and the star will collapse even quicker than it had been before. The star eventually becomes so dense that the neutrons touch each other, prohibiting further collapse. Because it is in such an unstable state, the star then expands rapidly, too rapid to stop, and matter begins to shoot into space. During this, there is a blast of energy from the core because of expansion, and it

sends a shockwave throughout the star, spreading matter further and quicker into space. This makes for extremely high temperatures and luminosity and for more heavy elements to be produced. Although the physical process of a supernova takes only seconds, the light from the event can last for months. As you can see, the light curves for the two different types of supernova vary slightly, with the Type I supernova peaking lower and gradually dimming, while Type II supernova peak much higher, but the peak drops quicker, and then it plateaus for a few months, before dimming again.
3)
As you can tell, supernovas are very powerful events that can produce a ton of energy and even heavy elements. At the end of the supernova activity, a Type II supernova would be able to produce all of the elements past iron that it hadn’t been able to create before. This is what causes most of the elements in the periodic table and the elements that make up life on earth. Supernovas are powerful events and they do, truly create life even in their death since they create new elements. So, now you know about the two different types of supernovas and what happens during them. You can also see that we are, due to the creation of the new elements in the explosion, in fact, stardust.