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Stellar Evolution

honors extra

                                      
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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 temperature-luminosity relation for stars, known as the the Hertzsprung-Russell diagram, shows stars on the main-sequence that 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 ofthe 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 timeusing the step button.

We have the following definitions:

Mass	Mass of the star in stellar masses.
Time	The age of the star in millions of years.

INSTRUCTIONS:

• Click on the star you want to evolve
  Or
• Choose the mass with the slider bar, and click "go".
  
• Use "clear" to remove unwanted, evolved stars.
• Use "stop/go" to stop and start the simulation,if desired.
  
• If the picture is messed up at anytime, use "clear"to redraw it.
  You must use "clear" if you want to"re-evolve" a star.
  
• Use "trail on" and "trail off" to leave the trail of the star through the H-R diagram.
  Hitting "trail off" will erase all trails of previously evolved stars. The last position is still shown.