The main sequence.
Stars spend the majority of their life span in the main sequence phase, which is a stable period of nuclear fusion where they convert hydrogen into helium. This phase can last for billions of years for stars like the sun.
When it is a young adult
Nobody "invented" it, the life cycle of stars happens naturally.
The "star life cycle" refers to stars. Earth is not a star.
In the nebula!
The smaller a star is, the longer its life cycle.
the answer is a protostar
The more the mass the shorter their life cycle (the more quickly they use their fuel)
Stars are "born", mature, reach old age, then "die".
Astro means star its study of the life cycle of stars
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The portion of a star's life cycle when it is using hydrogen for fuel is called the main sequence phase. This is when a star fuses hydrogen in its core to produce energy and maintain stability. Stars spend the majority of their lives in this phase.