stars that have roughly the same mass as the Earth's sun follow a similar evolutionary path, much of which lies along a general trend on a diagram of solar luminosity versus surface temperature (this diagram is called a Hertzsprung-Russell [H-R] diagram). The H-R diagram shows how a star's size changes as it evolves with respect to luminosity and temperature over time, with most stars the size of the sun following a curved s-shaped trajectory across the diagram, called the main sequence of stellar evolution. For about 90 percent of a star's evolutionary history it will burn hydrogen quietly without changing much and will remain close to stationary on the H-R diagram. However, a star's early and late stages of evolution can be quite different from its average or steady-state main-sequence characteristics. The evolutionary stages and track of a star are shown on the H-R diagram through its history of luminosity and surface temperature. stars with the mass of the sun go through several stages, from interstellar cloud, to collapsing interstellar cloud fragment, to protostar, to main sequence star.
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