Youtube! Edgar here! And welcome to Artifexian! Here you will learn everything you ever wanted to know about worldbuilding, and then some!
In this episode, let's look at the life cycle of a supermassive star.
A supermassive star is any star with a mass of at least 9 times that of our own sun.
Like before, a supermassive star will start life as a giant molecular cloud.
Gravity will cause the cloud to collapse, forming a protostar, and eventually with enough heat, the star will begin nuclear fusion.
The only difference is that in order to form a massive star, the initial cloud must also be very massive.
Due to their mass, very large stars will have a very large fuel supply,
but gravity's crushing pressure will force the star to burn through its fuel supply very rapidly.
So supermassive stars tend to live fast and die young.
A star will begin by simultaneously fusing hydrogen and helium for a few million years.
Once all the fuel has run out, it will then for the next few thousand years fuse carbon into neon.
Then, neon into oxygen for a single year. Then oxygen into silicon for a few months.
And lastly, silicon is converted into iron in only three to five days!
Throughout these fusion processes, the outer layers of the star will be expanding, and internally the star will be layered like an onion.
Every time a new element is used as nuclear fuel, any remaining unfused atoms will form layers around the core.
So why does this fusion stop at iron? Why can't iron be fused together?
Well, it can! But in order to fuse iron, energy is required to power the reaction rather than giving out.
This upsets the equilibrium of the star and causes it to become unstable,
Or in other words, the iron core drains energy from the star.
With the star no longer in equilibrium, gravity will cause the star to collapse, squeezing atoms closer and closer together.
This crush is temporarily stopped by electron degeneracy.
But due to the massive nature of our original star, gravity will soon overcome even the repulsive forces of electrons.
The crush will continue until something called electron capture occurs.
Here the gravitational forces are so immense that electrons are forced to collapse into the nucleus of the atoms.
They merge with protons, forming neutrons.
Gravity has now created a tiny, super-dense ball of neutrons at the core of the star.
This core of neutrons stabilizes because of neutron degeneracy. Gravity stops its crush, and equilibrium is created.
However, the collapse of the star's core into a ball of neutrons releases an enormous amount of energy outward in the form of neutrinos.
This will cause the outer onion-like layers of the star to violently explode outward into the cosmos.
This explosion is known as a supernova. During the explosion, material is ejected at 10% the speed of light!
The energy that this produces is enough to fuse iron, and thus all elements heavier than iron are created in supernovae.
Stars and supernovae are the elemental forges of the cosmos, creating everything we see around us!
To give you an idea of just how explosive supernovae are, if I blew up an amount of TNT equivalent to... one trillion times the mass of the Earth,
I would get an average supernova.
Supernova 2006-GY, the largest ever recorded, was produced when a star 150 to 200 times the mass of our own sun exploded.
Making a TNT analogy here is futile. The numbers are just too big to comprehend.
So the outer layers don't exist anymore, so what happens to the core?
Well if the star was between 9 and 20 times the mass of our own sun, the tiny core of neutrons, also known as a neutron star, is the star's final resting place.
Neutron stars are between one and three times the mass of the sun squeezed into an area the size of an average city.
Due to the fact that neutron stars are comprised solely of neutrons, they are enormously dense objects.
A teaspoon full of neutron star material would weigh a billion tons!
Some neutron stars spin very rapidly, and have a very strong magnetic field.
And as a result, charged particles are shot out of the star in beams of light.
When this occurs, the object is known not as a neutron star, but rather, a pulsar.
However, it gets weirder! If our original star had over 20 times the mass of our sun, even the forming of a neutron star won't be stable.
The core will be so massive that gravity will crush it into a single point of infinite density. This singularity is known as a black hole.
Nothing can escape the gravitational pull of a black hole, not even light.
So stars are kinda like celebrities. The brown dwarf is an object that had its 15 minutes of fame but faded to obscurity and lost its celebrity status.
And a low mass sun-like star is the Morgan Freeman of the cosmos, seemingly going on forever and reliably remaining constant throughout its life.
Finally, supermassive stars are celestial rock stars. They live fast and die young and go out with a bang!
But more importantly, their legacy will inspire the next generation to also strive for stardom.
So there you have it. The life cycle of a celestial rock star!
Guys! Like! And subscribe! Thank you so much for watching, Edgar out!
Also, big thanks to armed core for suggesting I slow down the talking a bit. Keep the comments coming guys! You guys make me better.