Nebulas are huge clouds of dust and gas, most of the gas that makes up the nebula is hydrogen. Sometimes nebulas can remain mostly static for billions of years. Eventually though a passing star or shock wave from a supernova will disturb the gas and dust. The dust and gas may then start to clump together, gravity will then clump more and more gas together, this is when the star starts the next part of its life cycle.
A protostar is when the gas has clumped together and it getting hot but has not reached what is known as critical mass. At this point the gas will be hot enough to glow. but since
there is still a large amount of dust surrounding the gas there isn’t much radiation given off in the visible spectrum(light humans can see)
A brown dwarf is when a protostar has not been able to reach critical mass, this means that fusion was never able to begin, these objects range in size from 13 90 times the mass of Jupiter.
Most stars in the universe for most of their life will fall into the category main sequence. A main sequence star is when a protostar is able to begin nuclear fusion, in the core of these stars hydrogen is fused into helium releasing energy in the process. Main sequence stars vary in size from around 0.08 the mass of our Sun (this is known as a solar mass) to 150200 solar masses In general the bigger a star is the faster it uses Hydrogen and the shorter it’s lifespan.
Depending on the stars mass it will either follow the path of a red giant or become a red super giant.
A star becomes a red giant when it has .5 5 solar masses. After the star has spent billions of years fusing hydrogen into helium it become a red giant. Because the helium is heavier it sinks to the centre of the star leaving a shell of hydrogen. After most of the hydrogen has been used the ...
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