1. By CJ B. Star Life Cycle

2. Protostars Stars begin to form out of a nebula Nebulas are a giant cloud of dust and gas (about 97% hydrogen and 3% helium) Within the gas cloud there are varying gravitational fields These fields collect atoms, the more atoms it collects the more mass it gathers and the more atoms it collects These clumps of atoms of dust and gas are called protostars Protostars are incredibly unstable because of the amount of reactions that occur within them constantly

3. Two Choices Remain At this point in a protostar’s life, it has two possible paths 1) It will never achieve equilibrium (and thus never achieve a constant temperature at it’s core) and it will turn into a Brown Dwarf 2) It will eventually reach equilibrium and thus be “born” because it has used nuclear fusion Stars are not considered “stars” until they have stared nuclear fusion

4. The Main Sequence Stars live out the majority of their lives on the Main Sequence Here, the star begins radiating energy into space (thus creating the shine) The star maintains nuclear fusion which gives it “fuel” to produce the shine The star slowly contracts over time to compensate for the heat and energy it continues to loose As this happens the star’s the star’s temperature, density, and pressure at the core increase The temperature at the center of the star slowly rises over time because the star radiates away energy The larger the star, the shorter the amount of time on the main sequence because although the star has more fuel, it also burns it off faster

5. After the Main Sequence After the main sequence, the star eventually dies The lifespan of a star is dependant on how big the initial mass of the star is The star will die once the hydrogen and helium in the core burn out, once this happens there will not be enough heat to fuse carbon Smaller stars (such as the sun) dies by puffing off its outer layers to produce expanding planetary nebulae Larger stars die in as little as millions of years, they develop dead iron cores and explode as a supernova

6. After Death The core of a dead larger star may become a neutron star or black hole, but the outermost parts of the exploded star return to the gas and dust they where born from Smaller star’s dead cores are turned into nebulae, and serve as birth place for other protostars to start

7. Bibliography Works Cited "Index of /labs/star_life." ASPIRE - Home. Web. 12 Dec. 2010..