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Life Cycles of Stars
Life Cycles of Stars
• Stars are born out of great clouds of gas and dust• They mature, grow old and die• They may produce new clouds of dust and gas• And planets• The more massive a star the shorter the life span
Hertzsprung - Russell Diagram
• A graph that plots luminosity against surface temperature
• The HR Diagram is much like the same thing as producing a graph of people’s height vs. weight.
• Main Sequence• Most stars 90 %• Extends from the hot,
bright, bluish stars in the upper left to cool, dim, reddish stars in the lower right
• Vary in temperature, magnitude and lifespan
• Giant Stars– 10 – 100 x’s diameter of
Sun
• Cool, luminous stars.– Luminous because of
large size.
• Supergiants– 100 x’s diameter of sun
• Bright due to size even though cool
• White Dwarfs• HOT but faint stars• Near end of life• Once Red Giants• The surface
temperatures of these stars are very hot, but since they are so small they are not very luminous
White Dwarfs
Supergiants
Red GiantsMain Sequence
Ab
solu
te
Mag
nitu
de
Bright
Dim
Lu
min
osity
O B A F G K M
Early Types
Hot
Late Types
Cool
Birth of a Star• Nebula condenses due to outside force• Force compresses gas and dust and the particles
move closer together due to gravity• Become– Denser– Hotter
• If large enough nebula will begin to glow• Protostar is born
Death of Sun like star
Death of Massive Star
Remnants of Stars• Supernova –
explosion of star– Neutron star– Gravity crushes
atoms electrons into nucleus
– 20 Km diameter– Trillion x’s as dense
as sun
• Pulsar • Rapidly spinning
neutron star• Gives off radio waves in
bursts• Like lighthouse light
• Black Holes• Remnant of a star at least
15 Solar Masses• Packed into 30 Km diameter
• Gravitational force so strong light cannot escape
• Give off x-rays when atoms are ripped apart
• Gravity of millions or billions of suns
