Life Cycle Of A Star

By: Grayden Sauerwein

What is this smore about?

In this smore, we will be comparing the life of a human to the life of a star. You would be surprised on how similar they really are. (Rhyming!!!)

Human vs Star Life Cycle

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What is an Interstellar Medium?

An Interstellar Medium put simply is the material the is in between stars. It is made up of mainly gas, like 99% of it is gas and then there is a little bit of dust there too.


The protostar is a slightly more dense ball of gas and dust that if it gets hot enough in the core of the star it will trigger Nuclear Fusion. Nuclear Fusion is when two elements under hot and dense conditions combine together to form a new element. The nuclear fusion creates enough outward energy to "fend off" the inward gravitational pull and this is described as equilibrium.

Main Sequence

Main sequence is the majority of the stars life and this is where nuclear fusion is still burning hydrogen (or deuterium) into helium. (An equation to describe this would be x+x=y or x+y=z). But some stars don't make it to this phase and others get out of it quickly because of their size. The bigger the star is the faster it will burn through its hydrogen supply and the size of that supply from the beginning will affect it as well. Similar to a bigger vehicle having fewer miles per gallon than a smaller one. At the end of this stage the star's outer layers will expand and will start to burn helium because it's hydrogen supply has run out.

Red Giant/Supergiant

As said at in the previous text box, at the end of the main sequence stage the star's outer layers will expand and will start to burn helium because it's hydrogen supply has run out. when the layers expand the internal core temperature gets hotter but the surface temperature gets cooler, the luminosity or brightness of the star is lower and there is less overall mass. The helium is fusing into much heavier elements like; carbon, neon, oxygen, iron, sodium, magnesium, and lithium.

White Dwarf

This is the last stage of a star's life. This occurs when the elements in the star have become too heavy to fuse or the core can't get hot enough to fuse them. Which means that the star cannot keep up the outward pressure needed for equilibrium. There are five ways for a star to die; planetary nebulae, supernovae, Black Hole, Brown Dwarf, and Neutron Star. What determines the way in which the star dies is its size, a larger star will produce a black hole, or a supernova, while a smaller star will be too small and have never gone through main sequence and just been a brown dwarf, or will be a neutron star or planetary nebula.


A supernova is produced sometimes when a large star dies. The core of the white star (Made of iron) collapses even further and this forms a neutron core, because it's so dense that the protons and electrons have merged to form neutrons. This in turn causes the core to heat to billions of degrees and then explodes, ejecting its matter into space.

Planetary Nebula

This forms similar to the red giant, except this occurs after it. The outer layers expand and cool again. The layers then get cast out into space around the dying star, forming the planetary nebula.

Star's Light

A star's light can tell you a lot about it. Like what it's composition is or what stage of it's life it is in. For example if you look up at the sky and find O'Ryan the Hunter you will see that his shoulder is red, the star that is in his shoulder is Betelgeuse, a red giant. Also in red giants they burn helium which has a more red spectra than hydrogen. There are a couple of terms that come into play when talking about the color and using it to identify the star better. Red-shifted and Blue-shifted. These terms are used to describe what direction a star is moving in, red-shifted is when the star is moving away from the earth and blue means it is moving towards. This is an example of the Doppler Effect.
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