How long does a typical star spend in the main sequence?

Scientists believe that time spent in the main sequence is one of the stages of a star's "life" Most known stars are main sequence stars. From this information, what can you infer about the amount of time a typical star spends in this stage?|||It's a population study. The parts of the diagram which have the most stars indicate the stages where they spend most of their lifetimes.





Here's a rough analogy. Suppose you have a snapshot looking down on a city from an airplane and you see a street that is several blocks long. The cars are fairly well distributed, but at three or four of the locations, you see serious crowding: large numbers of cars in a relatively short length of road. You would conclude that this is where they are stopped at red lights. In other words, these are places where they are spending longer than they do when on the roll.





Stars stay on the main sequence longer, the farther to the red end of the graph they are. The O and B stars, maybe only 100 million years or less. A, F, and G, stars would be from a couple billion to about 10 billion. K and M stars, probably dozens of billions of years.|||Roughly...


Tms = 10 billion years / (M/Msun)^2.7|||You can infer how long a star of a given mass will be on the Main Sequence, which is the stage of life where a star fuses hydrogen into helium for energy. It has also been determined that all stars spend some 80 or 90 percent of their active lifetimes as Main Sequence stars generating their own energy internally. How long a star lasts as a Main Sequence object is directly dependent upon it's mass and to a much lesser degree the chemical composition it started it's life with. The more massive the star, the less time it can last as a Main Sequence object. As the mass increases, the surface temperature, the diameter and the luminosity also increases. The more massive a star, the more violently it's death will be. As for what a typical star is, it's most certainly not a blue giant such as Rigel, nor is it a star like the Sun or Alpha Centauri A. It's a red dwarf, which comprise some 75 percent of all stars. The Sun was born with enough fuel to spend 10 billion years or more on the Main Sequence, but the average red dwarf will last a trillion years even though it could be less than 20 percent of the Sun's mass. They are long lived because the pressure in their cores is barely enough to start and maintain nuclear fusion, and thus they do not have to generate much energy to support themselves against their own gravity. Massive stars have to generate huge amounts of energy to oppose their own gravity, and thus rapidly exhaust their fuel even though they can start out with 100 times the Sun's mass. This results in a luminosity that can exceed the Sun 50,000 times over, but also results in a life span of a mere 10 million years or less.