Hi! Yes, you! You're a star.
Literally.
Let me explain by starting at the very beginning.
When the Big Bang had just happened,
the only elements in our hot, dense universe were
hydrogen, helium, and trace amounts of beryllium and lithium.
But... don't we require oxygen to breathe?
Our blood has iron in it, and our bones have calcium.
So, where are they?
Well, life didn't begin when the universe was created.
No, for life, we need stars!
Stars are formed from stellar nebulae - huge clouds of gas and dust that come together due to gravity.
Before it's a fully grown star, it's
called a protostar, which is a clump of
gas and molecules that might eventually
become a brown dwarf or successfully become a star!
In its first stage, it's called a main-sequence star.
This is because what keeps the star "living" is a delicate battle between
the outward radiation pressure of fusion and the inward pressure of gravity.
This fragile balance between the two competing forces is called the hydrostatic equilibrium.
All stars fuse hydrogen into helium for
nearly 90% of their lives.
For an average-sized star, like our Sun, the
temperature and gravitational pressure
at the core won't be very high. So the
star can kinda chill,
taking billions of years to run out of fuel.
When it's nearly done, the hot core will shrink and
the extra energy pushes the surface of
the star outward. It is now a red giant!
As more of the outer layer, or planetary nebula, is pushed away,
What is left in the middle, is the white dwarf.
Let's talk about massive stars.
Bigger isn't always better, as their lives are much shorter,
although definitely more exciting.
As they run out of hydrogen and their core shrinks, temperatures are large enough to fuse
heavier elements in smaller time periods.
For this star, the main sequence lasts a mere 7 million years.
Then, helium forms into carbon, carbon fuses into oxygen, which fuses into silicon, then iron and then BOOM!
The star collapses within 1/4 of a second in a brilliant, bright supernova explosion!
This is because iron cannot be fused, so
gravity wins!
But wait, there's more!
The extreme temperatures and pressures
cause the creation of elements heavier
than iron with higher atomic numbers -
uranium, gold, mercury, silver, zinc, phosphorus, sulphur -
And, all of this is spewed out great distances in the magnificent supernova explosion.
After this, the star might become a neutron star, or if the core is even more massive, a black hole!
So, human life originated from the stars, but not until the supernova stage.
This means that a star had to die, for you to be born.
So, if you ever feel bad about yourself again, just remember that
"you are made of starstuff." - Carl Sagan :)
