The Cycle Of Stars Flashcards
What do stars initially form from?
Dust and Gas.
What does the force of gravity do to the gas and dust?
It makes them spiral in together to form a protostar.
What is gravitational energy converted into?
Heat energy.
So the temperature rises.
What happens when the temperature gets high enough?
Hydrogen nuclei undergo nuclear fusion to form helium nuclei.
What else happens when hydrogen nuclei undergo nuclear fusion?
Massive amounts of heat and light is given off.
What do smaller masses of gas and dust do?
Pull together to make planets that orbit the star.
The star immediately enters what?
Long stable period.
What does heat created by the nuclear fusion provide?
An outward pressure to balance the force of gravity pulling everything inwards.
How long does the star maintain its energy output?
Millions of years .
The star maintains its energy output for millions of years because why?
Its due to the massive amounts of hydrogen it consumes.
In the stable period what is it called?
Main sequence star.
Last several billion years.
Eventually the hydrogen begins to what?
Run out.
Heavier elements are made like?
Iron.
Heavier elements are made by what?
Nuclear fusion of helium.
The star then swells into what?
Red giant - small star.
Red super giant - big star.
Why does it become red?
Because the surface cools.
When a small-to-medium star like the sun becomes unstable what happens?
It ejects its outer layer of dust and gas.
The ejecting of the outer layer of dust and gas is what?
Planetary Nebula.
What does a planetary nebula leave behind?
Hot dense solid core.
White dwarf.
The white dwarf cools and does what?
Becomes a black dwarf.
Disappears.
Big stars however start to do what?
Glow brightly again as they undergo more fusion.
The big stars undergo more fusion and what else?
Expand and contract several times.
The big stars also from what?
Heavy elements like iron.
What do the big stars eventually do?
Explode in a supernova.
When the big star explodes what does it form?
Elements heavier than iron.
When the big star forms heavier elements what does it do?
Ejects them into the universe to from new planets and stars.
The exploding supernova throws what?
Outer layers of dust and gas into space.
The supernova leaves a what?
Neutron star.
If the star is big enough it will leave a what?
Black hole.
The early universe only contained what?
Hydrogen.
Simplest and lightest element.
