Chapter 19-2
Life Cycle of Stars
The Beginning of StarsBall of gas and dustGravity pulls the gas and dust together into
a sphereAs density increases, so does the
temperatureHydrogen changes to helium (nuclear
fusion)
Main SequenceThe second and longest stage of its life
cycleDuring this time,
nuclear fusion releases enormous amount of energy
the size changes very little
Red GiantsA large, reddish star late (3rd stage) in its
life cycleCreated when hydrogen is “used up”,
which causes:the core to shrinkthe atmosphere to become largethe star to cool
Can be 10 or more times biggerthan our sun
Red SupergiantsForm the same way as red giantsAre at least 100 times bigger than the sun
White DwarfsA small, hot, dim star that is the leftover
center of an old starCan shine for billions of years before
cooling off completely
Average Stars Larger StarsMain Sequence
Red Giants
White Dwarfs
Main Sequence
Red Supergiants
Supernova
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SupernovaA gigantic explosion in which a massive
star collapses and throws its outerlayers into space
• Comes from massive blue star• Can be brighter than an entire
galaxy
Leftovers of SupernovaNeutron Stars and
PulsarsBlack Holes
Neutron Stars and PulsarsNeutron Star: a star that has collapsed
under gravity to the point that the electrons and protons have smashed together to form neutronsComes from the materials in the center of a
supernova being squeezed together
Pulsar: a rapidly spinning neutron star that emits rapid pulses of radio and optical energy
Black HolesForms when the leftovers of a supernova
are incredibly massiveBlack Hole: an object so massive and
dense that even light cannot escape its gravity
H-R diagram