Astronomy 1101/1103 __________________________ Terry Herter

Example to try

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The determining factor in the life of a star is its mass. The more massive a star the greater its energy output and the faster it evolves (changes).

The about figure shows the temperature-luminosity relation for stars. This is known as the the Hertzsprung-Russell diagram. Stars on the main-sequence generate energy by converting (via fusion) hydrogen into helium. As stars use up their hydrogen fuel, they evolve off the main-sequence into the giant or supergiant phase. During these stages stars may "burn" helium or other even heavier elements as the core of the star reaches higher and higher temperatures and densities. How far this process proceeds depends on the initial mass of the star. The lowest mass stars will never go beyond hydrogen burning while the highest mass stars can produce elements all the way up to iron in their cores.

The above simulation shows the evolution of a star in the H-R diagram. To see a star evolve, simply click on the star or choose a mass with the slide bar and press go. The total evolution of the star will take place over a period of 10 seconds, with the star spending the correct relative amount of time at each step. You can also proceed through the evolution one step at a time using the step button.

We have the following definitions:

Mass Mass of the star in solar masses.
TimeThe age of the star in millions of years.



Please note: