Stars start their life cycle when they’re being formed in clouds of gas and dust, which are known by astronomers as nebulae.
Nuclear reactions at the core (center) of stars provide them energy, which makes them shine brightly for hundreds of thousands to billions of years.
This stage of a star’s life cycle is known as the main sequence.
The exact lifetime of a star depends very much on its size.
The process is also commonly called the stellar life cycle.
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Mass determines the life cycle of a star
A star’s life cycle is determined by its mass. The larger its mass, the shorter its life cycle. And the lower its mass, the longer its life cycle.
This is because larger, more massive stars burn their fuel more quickly than smaller stars. As a result, they may only last a few hundred thousand years.
Smaller stars, on the other hand, can last for several billion years, as they burn their fuel at a slower pace.
This image courtesy of NASA shows the life cycle of a star.
Nuclear reactions within stars are powered by hydrogen fuel.
Eventually, this fuel begins to run out.
When this happens, stars enter the final phases of their life cycle.
As their final phase plays out, they expand, cool, and start to change color. This is the point at which they become known as red giants or supergiants.
Their path from that point forwards depends on their mass.
The Life Cycle of Stars
The life cycle of the Sun
The Sun in our solar system is a small star. The Sun will undergo a fairly monotonous death.
It will go through a planetary nebula phase in which it will become a white dwarf.
As a white dwarf, the Sun will eventually cool over time. Then it will stop glowing and become what’s known as a black dwarf.
The life cycle of massive stars
Massive stars that exist in other solar systems, on the other hand, will experience a more violent ending.
These end in what’s called a supernova, which is a cosmic explosion that releases its material across the solar system.
Once all the cosmic debris clears, it will be left with a very dense star known as a neutron star.
Sometimes neutron stars spin and are known as pulsars.
If a star is very large and explodes, it can even form a black hole.
A black hole is an area that has a high gravitational pull but emits no energy.
In this case, the gravitational pull is so strong that no particles, matter, or even electromagnetic radiation such as light can escape from it.
The Life and Death of Starts: White Dwarfs, Supernovae, Neutron Stars, and Black Holes
A good primer on white dwarfs, supernovae, neutron stars, and black holes.