By Huzayfa Mallick
When you look up at the sky on a clear night, depending on where you live, it’s possible to see stars (and even galaxies) shining brightly from time to time. Unfortunately, if you live in a massive city, you’re likely to only see a few stars here and there. However, a place without any light pollution can provide a great view of the night sky.
There are two main types of supernovae: thermal runaway and core collapse. In this article, we will be focusing on core-collapse supernovae.
In the picture above, you can see stars from across the universe, some visible from millions of light years away. All these stars follow a similar life cycle, for the most part, starting off from a nebula. However, only the massive stars eventually go through an explosion famously known as a supernova! The explosion of a massive star leads to a powerful burst of energy and light that can often be seen across galaxies. But how exactly does a supernova work? What is the science behind the explosion of a massive star and what does it leave behind?
To understand why a star reaches the supernova phase, we need to go over how a star operates in the first place. Nuclear fusion is the process that stars use to sustain themselves, acting as fuel for the star. For the majority of its life, a star fuses hydrogen into helium (shown in the diagram below), providing the star with the fuel and energy that it requires. In addition to serving as fuel, the energy produced in the nuclear fusion reactions also counteracts the gravitational force on the star, thus providing a delicate balance to keep the star from collapsing. The balancing of the forces is shown in a diagram below.
With the constant process of nuclear fusion providing the star with energy, it is inevitable that the star will eventually run out of hydrogen to use in the fusion process. This marks the ‘beginning of the end’ for the life of a star. At this stage, the star typically expands and transforms into a larger red giant. Remember, the goal of nuclear fusion is to provide fuel for the star, as well as to keep the star from collapsing from the gravitational force that it faces. Thus, in an attempt to sustain itself, the star begins to fuse heavier elements to produce the energy that it needs. When it reaches the element iron, the process of nuclear fusion requires energy instead of producing it for the star to use, marking the end of the star’s life.
As the process of nuclear fusion no longer produces the energy that the star needs for fuel (or the energy needed to resist the gravitational force it faces), the star collapses towards the core. The elements of the star essentially bounce off the core and are released into space as a powerful explosion, packed with massive amounts of energy and light.
With that being said, it is important to note that only massive stars, much larger than our Sun, have the ability to enter the supernova phase. Smaller stars go out in a less dramatic fashion, typically ending up as white dwarfs at the end of their life cycle (not having the ability to go supernova). On the other hand, for the massive stars that enter the supernova phase, it’s still far from the end. The stars that are ‘less massive’ usually end up as neutron stars. For stars that are extremely massive, they end up as black holes at the end of their life cycle.
That’s all for this week’s blog on the science behind supernovae. Check back next week for another blog on the topic of Aquaponics.
References
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The National Aeronautics and Space Administration. (n.d.). Stars | Science Mission Directorate. NASA Science. Retrieved September 8, 2023, from https://science.nasa.gov/astrophysics/focus-areas/how-do-stars-form-and-evolve
The National Aeronautics and Space Administration.(n.d.) What holds a star together? [Photograph]. Nasa Science. https://spaceplace.nasa.gov/supernova/en/supernova2.en.jpg
The National Aeronautics and Space Administration. (2013, September 4). What Is a Supernova? NASA. Retrieved September 8, 2023, from https://www.nasa.gov/audience/forstudents/5-8/features/nasa-knows/what-is-a-supernova.html
The National Aeronautics and Space Administration. (2017). [Photograph showing a supernova]. Scientific American. https://static.scientificamerican.com/sciam/cache/file/C3AF4333-C48A-48C9-851C12EF5C8D1F4D_source.jpg?w=390&h=520&5425D0AE-6B8B-49E5-AE9012F05111EAD8
The Schools' Observatory. (n.d.). Life Cycle of a Star. The Schools' Observatory. Retrieved September 8, 2023, from https://www.schoolsobservatory.org/learn/astro/stars/cycle
Thompson, A., & Hickok, K. (2023, June 19). What is a supernova? Space.com. Retrieved September 8, 2023, from https://www.space.com/6638-supernova.html
U.S. Department Of Energy. (n.d.). DOE Explains...Supernovae. Department of Energy. Retrieved September 8, 2023, from https://www.energy.gov/science/doe-explainssupernovae
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