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The Question

(Submitted January 02, 1999)

I was wondering what the types of stars were? I only know a few, such as white dwarf, and red giant.

The Answer

About 90 percent of the stars lie in the H-R diagram, marked by the main sequence: http://zebu.uoregon.edu/~soper/Stars/hrdiagram.html

A star shines by radiating energy from the nuclear reactions. Once a star runs out of its fuel, it dies and becomes compact. The lifetime of a star depends on its mass. High-mass stars evolve faster and die sooner than low-mass stars. The most massive stars may live only a few million years, and the lowest mass stars can live 100's of billions of years.

Low-mass stars die quietly, while high-mass stars die in tremendous explosions (supernovae explosions). A star like our Sun would die and end as a white dwarf:

http://imagine.gsfc.nasa.gov/docs/introduction/dwarfs.html

Stars about five to ten times more massive than our Sun would explode and form a neutron star. More massive stars turn into black holes:

http://imagine.gsfc.nasa.gov/docs/ask_astro/neutron_star.html
http://imagine.gsfc.nasa.gov/docs/ask_astro/black_holes.htm

Samar Safi-Harb & David Palmer
for Ask an Astrophysicist

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