Honors 1500 - It= s About Time

 

The Spectral Sequence

high mass, bright, hot, short MS lifetimes <B O B A F G K M B > low mass, dim, cool, long MS lifetime

(MS = main sequence on the Hertzsprung-Russell diagram)

 

Summary of Stellar Evolution

all stars

interstellar cloud of gas (mostly hydrogen and helium), ices, and dust

cloud undergoes gravitational collapse to form a protostar

protostar=s center becomes hot enough for nuclear fusion reactions

fusion of hydrogen nuclei (protons) B > helium nuclei begins in the protostar=s core

newborn star on the main sequence of the Hertzsprung-Russell diagram

time passes: 10 billion years for a low-mass G star (our Sun)

15 million years for a high-mass B star

all hydrogen available for fusion in center converted into helium

star's core contracts and heats, surface expands to become a red giant

fusion of helium nuclei B > carbon and oxygen nuclei begins

all helium available for fusion in center converted into carbon and oxygen

star becomes a red supergiant

low-mass star
 

intermediate-mass star
 

high-mass star
 
inert carbon-oxygen core
 
more fusion produces inert iron core
 
more fusion produces inert iron core
 
outer layers of red supergiant ejected to form a planetary nebula
 
core of red supergiant collapses to form a supernova
 
core of red supergiant collapses to form a supernova
 
carbon-oxygen core remains as a white dwarf
 
neutron core remains as a neutron star
 
neutron core collapses to form a black hole
 
white dwarf cools and crystalizes neutron star cools  

 

 

 

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Last modified:  Sunday, April 24, 2005 04:16 PM

 

 

 

 

 

 

  • low-mass star intermediate-mass star high-mass star

  • inert carbon-oxygen more fusion produces more fusion produces

  • core inert iron core inert iron core

    outer layers of core of core of

    red supergiant red supergiant red supergiant

    ejected to produce collapses to produce collapses to produce

    a planetary nebula a supernova a supernova

    carbon-oxygen core neutron core neutron core

    remains as a remains as a collapses to form a

    white dwarf neutron star black hole

    white dwarf cools neutron star cools

    and crystalizes