Stars

Before the first star  Early Universe, Matter is cooling  Finally Forms first atoms - H  This is 400,000 years a.b.b.  Early Universe, Matter is cooling  Finally Forms first atoms - H  This is 400,000 years a.b.b.

Hydrogen, so what?  Nothing but hydrogen makes for a boring universe…  Or does it?  What will all that H do?  Nothing but hydrogen makes for a boring universe…  Or does it?  What will all that H do?

Just a theory…

Finally  It takes 399,600,000 years after the first H atoms appear.  A mass of hydrogen atoms reaches critical density and pressure  Ignition!  It takes 399,600,000 years after the first H atoms appear.  A mass of hydrogen atoms reaches critical density and pressure  Ignition!

Recipe for a Star  97% hydrogen, 3% helium (and traces of heavier elements) in the form of:  Dust and gas from the Interstellar Medium  Concentrate into a nebula  Add gravity and let it compress!  97% hydrogen, 3% helium (and traces of heavier elements) in the form of:  Dust and gas from the Interstellar Medium  Concentrate into a nebula  Add gravity and let it compress!

Ignition of what?  What do we get from the sun?  Light, heat, etc.  Must come from somewhere…  How is it produced???  What do we get from the sun?  Light, heat, etc.  Must come from somewhere…  How is it produced???

This sucker is nuclear???

Yes! Nuclear Fusion!

Real Ultimate Energy  Nuclear Fusion produces energy according to Einstein’s equation  E = mc 2  Hydrogen is the fuel  Nuclear Fusion produces energy according to Einstein’s equation  E = mc 2  Hydrogen is the fuel

Find Balance…  Hydrogen fusion = the “Main Sequence”  Intense energy production from fusion creates outward pressure.  While immense amounts of gravity pull everything inward!  This state where these intense forces are balanced is called “Equilibrium”  Hydrogen fusion = the “Main Sequence”  Intense energy production from fusion creates outward pressure.  While immense amounts of gravity pull everything inward!  This state where these intense forces are balanced is called “Equilibrium”

How long will it last?  Depends on the star  As we can easily tell just by looking up at night, not all stars are the same  A stars lifespan depends on its size.  Why?  Depends on the star  As we can easily tell just by looking up at night, not all stars are the same  A stars lifespan depends on its size.  Why?

The Brightest Flame Burns Fastest…  Some blue supergiants will last only a couple hundred million years  While some red dwarfs may last into the trillions of years  Our sun has been going for about 5 billion years, and should go for about 5 billion more!  Some blue supergiants will last only a couple hundred million years  While some red dwarfs may last into the trillions of years  Our sun has been going for about 5 billion years, and should go for about 5 billion more!

Nothing lasts forever.  Eventually the star runs out of hydrogen and fusion stops.  There is less outward pressure and the star begins to compress further.  This then raises the temp enough to begin fusing HELIUM!  Helium fusion is Hotter than Hydrogen.  So there is more outward pressure – Red Giant!  Eventually the star runs out of hydrogen and fusion stops.  There is less outward pressure and the star begins to compress further.  This then raises the temp enough to begin fusing HELIUM!  Helium fusion is Hotter than Hydrogen.  So there is more outward pressure – Red Giant!