The Life Cycle of Stars

The different phases stars go through during their existence

Before the Begining

Before a star can even be created, there has to be space. This space, is called the Interstellar medium. Essentially it is the empty space between stars, which is basically outer space. It's primarily made up of gas, and dust.

Protostars

Protostars are the very, very beginning of a star. It's a mass of dust and gas, clumped in one spot. It has enough mass to have it's own gravity, and there is enough "stuff" inside it, and enough heat, that it builds up pressure. This is when gravity and pressure struggle for dominance over the other. Once the two finally equal out in power, the star has reached equilibrium. Meaning that the force of its gravity is equal to the force of its pressure.

The Main-Sequence

The elements present during the main stage are Hydrogen, and Helium. During this stage, Thermonuclear Fusion of Hydrogen begins. The thermonuclear fusion of Hydrogen is caused by the immense pressure, and gravity inside the star. The temperature and density of the stat determine how long this stage will last, as well as the color of the star. At the end of this phase, all the Hydrogen is burned up, and the Nuclear fire is extinguished.

Red Giants

The elements present during this stage are: Helium, Oxygen, Carbon, and Beryllium. The gravity of the star battles against the power of the fusion reaction, and wins. Thus, the core of the star is crushed inward, and the outer layer of the star expands. The thermonuclear fusion of Helium happens during this stage. The temperature, volume, and luminosity increase during this stage.

The Beginning... of the End.

The Red Giant dies due to loss of Helium during thermonuclear fusion, essentially it ran out of gas. Stars can die so many ways, much like people. Some of the ways stars die are; turning into white dwarfs, black dwarfs, a neutron star, go through a supernova explosion, or turn into a black hole.

Supernovas - The Beginning again.

Supernovas happen when a stars gravity becomes so much stronger than the stars pressure, that by pressing inward, everything inside the star rapidly escapes all at once, causing an explosion. The only thing left after a supernova is the stars core, dust, and some gas. The gas and the dust, once settled creates a planetary nebula, the very inkling of a star.

Light, Stars, and Christian Doppler.

Actual Color: The actual color of a star during its main sequence depends on its density/temperature. If the star is relatively cool, it is red/orange. If however, a star is very hot, even for a star, it is blue/white. Think about when you look at a fire, the red and orange parts of it aren't as hot as the tiny blue flame at the top.


Perceived Color: Now even though a star is blue, doesn't mean we'll see it as blue. This is caused by the Doppler Effect. The Doppler Effect happens when an object omitting waves on the electromagnetic spectrum moves, the waves bend around the object. As we know with visible light, the higher the frequency, the cooler the color. This happens to stars as well. Some stars are moving towards are earth, and others away. Now because the star is traveling to our earth, the light waves bend around it, sending a higher frequency to the direction its going, and a lower frequency the direction it's not going. This means, that the color of the star perceived by our eyes, on earth, depends on whether or not the star is travelling towards us. If the star is traveling towards us, the perceived color is blue, and if the star is traveling away from us, the perceived color is red.