describe in general the life history of a star with an average mass like the sun

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For a star around the size of our Sun: Gas --> Star --> Red Giant --> White Dwarf --> Black Dwarf Stars of .4 up to about 1.4 solar masses are the main sequence stars often called yellow dwarf stars. This is the most common type of star and includes our sun. These stars will live about 10 billion years. Gasses, mostly hydrogen, from the deaths of other stars (Nova and Supernova) begin to collect together. The mass of gas gets bigger which increases the gravity of the ball of gas and pulls in more gasses. The gravity pulling in the gas causes the gas in the center to be compressed under huge pressure. This causes the temperature to increase until the hydrogen ignites in nuclear fusion. Once the star's core begins nuclear fusion, the outward forces produced by the fusion reactions balance the inward forces of gravity creating equilibrium. This is the main stage of star’s life. With these stars, as they age they will burn up much of their hydrogen. Once this happens, the burning in the core starts to slow. This reduces the outward forces and causes the star’s gravity to begin contracting (squishing) the core. This causes the core to heat up further until it gets hot enough to begin another fusion reaction--burning the helium in the core into carbon and oxygen. At this time, the heat causes some of the remaining hydrogen in the shell of the star to begin fusion reactions outside the core. All this burning causes an outward pressure once again which causes the outer layers of the star to begin expanding. The star will expand to over 200 times it former radius and becomes a red giant star. When this happens to our sun in about 5 billion years, it will grow out until it engulfs most of the inner planets, possibly even the earth. After about 100 million to 500 million years as a red giant, the helium in the core will run out. The mass and temperature will be too small to fuse any of the carbon or oxygen. The outer layers will leave the star (and become a nova) and the remains of the core will become a white dwarf—a small but extremely dense star about the size of the earth but much, much more massive. The white dwarf is very hot, and slowly begins to cool. It is so hot and massive, it takes a long time to cool. After about 10 billion years of cooling, it will finally become a cold, dead black dwarf.

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