Star Life Cycle

By Cole Dube

Before a Star is Born - Interstellar Medium

The interstellar medium is the material between the stars. Its made up of gas and dust, gas being 99% of the matter.

Protostars - First Stage of a Star

Protostars are the first stage of a star. Within a nebula, gravity pulls in gas and dust from the interstellar medium. As the nebula gets more mass the gravitational pull increases allowing for more and more mass to be pulled in to the clump. The nebula mainly consists of hydrogen (97%) and helium (3%).

Comparing this to humans would be like a growing fetus.


The main goal of a stars life is to achieve equilibrium. Equilibrium is when opposing forces are balanced. In this case the two apposing forces are the gas pressure pushing outward from the center and the gravity pulling atoms in toward the center.

Once stars have reached equilibrium fusion will stop after a while due to the lack of hydrogen, and the core temperature will drop. Gas can't resist gravity anymore so the star begins to contract. As the core shrinks the atoms become tightly packed and they start gaining heat. The core keeps gaining heat until it can begin nuclear fusion again. This cycle continues until all of the hydrogen is gone.

Main Sequence

The main sequence is like childhood through middle aged adulthood for humans. Stars stay here most of their life and the length they stay here depends on how long it takes to burn up all of their hydrogen. During the main sequence they are in equilibrium and burning hydrogen.

Red Giant

Red Giant stars are like middle aged humans. The temperature rises, the luminosity lowers and the star expands. During the stars stage of being a red giant they fuse helium into carbon.

Star Death

Like humans, stars get old and die too. A star dies when all of its fuel burns up and there is nothing else to fuse. When a star dies it could become a white dwarf, a planetary nebula, a black hole, a supernova, or something else. What it becomes depends on how big the star is. Massive stars much bigger than our sun produce supernovae. A planetary nebula is created when a star blows off its outer layers and leaves a ring in space.

The Role of Star's Light

Stars light reveals its composition through its electromagnetic spectrum. A star can be tinted different colors through age. The Doppler Affect has an example from stars. The farther you get away from the sun, the dimmer the light is.

The Origin of the Elements

Elements come from supernovae, the big bang, nebula, and other places. For example hydrogen comes from the big bang, iron comes from large stars and supernovae, and nitrogen and oxygen comes from small and large stars.


Works Cited

"Stars - Main Sequence." Stars - Main Sequence. N.p., n.d. Web. 23 Mar. 2015.

"What Is the Interstellar Medium?" What Is the Interstellar Medium? N.p., n.d. Web. 23 Mar. 2015.

"White Dwarfs, White Dwarf Stars Information, Facts, News, Photos -- National Geographic." National Geographic. N.p., n.d. Web. 23 Mar. 2015.