Life Cycle of Stars

by Lydia Pinard

How is a Human Life Cycle Like a Stars?

They both go through similar phases of growth. Fetus, Infancy through Adulthood, Middle Age, and Old Age-Death.
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Stage 1: Protostar

The Protostar is like the fetus phase of human life. This is where the stars have just formed and are brand new. Protostars form from nebulae. At this point the stars are made of hydrogen mostly (97%) and helium (3%). During the Protostar phase the star reaches Equilibrium. Equilibrium is the balance between gravity pulling atoms to its center and pressure pushing heat light away from it.

Stage 2: Main Sequence

During the main sequence the star slowly contracts in order to make up for lost heat and energy. At the same time, the star's temperature, density, and pressure increases. The temperatuer continues rising until it's core radiates away energy. After this it becomes a red giant.

Stage 3: Red Giant

The star's size continues to grow and the temperature continues to increase rapidly. Helium burns throughout the core, whilst hydrogen reactions (fusion, the burning of hydrogen) occur in the outer layers of the star. Once the helium is all burnt out the star (begins to) dies.

Final Stage: Death

There are many ways a star can die/what they become after death. Stars die when they run out of fuel. In death, some stars become planetary nebulae, white dwarves, black holes, and supernovae/nuetron stars.

Spectroscopy (What does a star's light tell us?)

Spectroscopy is the study of a star's light. It can tell us a star's temperature, chemical makeup, wavelength, and frequency (based off star's color).

Where Do The Elements Come From?

The elements on the periodic table come from many places. These places are small stars, large stars, the big bang, and supernovae.

Some examples:

Hydrogen- big bang

Iron- supernovae

Oxygen-small stars and large stars

Nitrogen-Small stars and large stars


"Life Cycle of a Star." Life Cycle of a Star. N.p., n.d. Web. 23 Mar. 2015.

N.p., n.d. Web. <>.

"Star Narration." Star Narration. N.p., n.d. Web. 24 Mar. 2015. <>.

(Also used 3 in-class packets)