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The Question
(Submitted February 25, 1997)
I would just like to know what the life cycles of the stars are.
Where they came from, and their life cycles,
and an explanation of the Hertzsprung-Russell diagram.
The Answer
We primarily study the compact remnants of stars, not the evolution of
stars. However, we can give a brief overview. Stars form from dense gas,
usually in molecular clouds. After a star forms, it burns hydrogen into
helium. It does this until the hydrogen begins to run out and then further
stages of burning occur, i.e., helium burns into heavier elements. If the
star is less massive than several times the mass of the Sun, it will
eventually become a white dwarf. If it is more massive than this it will
first implode and then explode in a supernova explosion. While the star is
still burning hydrogen it is on the Main Sequence of the H-R diagram, which
is a plot of temperature versus luminosity for stars. When the star is done
burning hydrogen, it enters other regions of the H-R diagram such as the
"Horizontal Branch", "Giant Branch" and "Asymptotic
Giant Branch". For
more info, check out http://zebu.uoregon.edu/~soper/Stars/hrdiagram.html (http://zebu.uoregon.edu/%7Esoper/Stars/hrdiagram.html)
Cheers,
Andy Ptak
for the Ask a High-Energy Astronomer team
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