Though the stars seem fixed and constant in the night sky, they, like us, are born, grow and change. The stages a star goes through over time are collectively called the life of the star.
Protostar
A star is born from a molecular cloud in space. The spiral arms of certain galaxies serving as nurseries. Dense sections begin coming together, eventually forming a protostar.
Birth
As the protostar collects matter--a process known as accretion--it heats up. when it reaches 15 million C, nuclear fusion begins, and hydrogen gases fuse to make helium.
Main Sequence
Once fusion starts, the star releases energy and begins to shine. This phase of a star's life is called a main sequence. The sun is a main sequence star.
Aging
During its main sequence, a star contracts, making its core temperature rise. Meanwhile, the hydrogen has fused into helium. Then the helium begins fusing into carbon.
Red Giant
With the helium fusing to carbon, the star expands and cools. It now has become a red giant. Red giants don't shine as brightly as main sequence stars.
Out of Fuel
Once the star exhausts its fuel, which takes millions upon millions of years, what happens next depends on the size of the star. A low-mass star would turn into a white dwarf. A star of medium mass would go supernova, then turn to a neutron star. Massive stars would become black holes.
Tags: main sequence, main sequence star, sequence star