StarsStars

Before the first starBefore the first starEarly 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?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…Just a theory…

FinallyFinallyIt 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 StarRecipe for a Star97% hydrogen, 3% helium (and traces of

heavier elements) in the form of:Dust and gas from the Interstellar MediumConcentrate into a nebulaAdd gravity and let it compress!

97% hydrogen, 3% helium (and traces of heavier elements) in the form of:

Dust and gas from the Interstellar MediumConcentrate into a nebulaAdd gravity and let it compress!

Ignition of what?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???

This sucker is nuclear???

Yes! Nuclear Fusion! Yes! Nuclear Fusion!

Real Ultimate EnergyReal Ultimate EnergyNuclear Fusion produces energy

according to Einstein’s equation

E = mc2

Hydrogen is the fuel

Nuclear Fusion produces energy according to Einstein’s equation

E = mc2

Hydrogen is the fuel

Find Balance…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?How long will it last?Depends on the starAs 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 starAs 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…

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.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!