Download - Life Cycle of Stars
26.2
3/27/07
Star Stuff
Forming a StarNebulacloud of dust and gas
protostar(takes 50 million years)
Contracts and rotates to form a ________
A Star is Born!
•A star when ______ startsfusion
10
• Hydrogen atoms combine to form Helium, other atoms• Takes ___ billion years to form
Adult Stars•Called “main sequence” stars•Longest period in life cycle•How long depends on star mass
A Balancing Act• Two forces act on
stars•Outward force from energy released by nuclear fusion
•Inward force from gravity
Old Age• Hydrogen fusion
slows• Gravity contracts
core• Core temperature
rises• Helium fusion
starts, releasing even more energy
Small Stars
•Mass of our sun•Fusion forms Helium, some Lithium, Carbon and Oxygen
•Last up to ___ billion years10
Small Star Old Age Red Giant
• Helium fusion when H atoms used up– produces heavier atoms – carbon &
oxygen
• Temperature rises with Helium fusion• Outer layers expand• Lasts ____ million years100
Small Star Death
•Hydrogen & Helium used up
white dwarf
planetary nebula
• Outer layers expand to form a ________ _______• Star core cools and contracts to form a dim _____ _____
Large Stars•6 x mass of our sun, or more•Fusion forms Helium, some Lithium, Carbon, Oxygen and Iron
•Last up to ___ million years10
Old Massive Star SUPERGIANT!
•Can be 100 x larger than our sun
•Hydrogen used up•He fusion in core produces
heavier atoms•Finally, core made of Iron
Dying Large Stars•Hydrogen gone - fusion stops•Core collapses, then rebounds
with explosion•SUPERNOVA!•Lasts few seconds
After Supernova…
•If mass 1-3 x the sun, final stage is _______ ____neutron star
pulsar
dense
• Protons and electrons collapse together to form ________ neutrons• Very ______
• Called ______ if rotating
After Supernova 2…
•If mass > 3 x sun, final stage is _____ ____black hole
gravitydense
• Extreme ______• Very ______
• No light escapes from it