8 The life of a star
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How are stars classified?
By their colour
What affects the colour of a star?
Its temperature
How does temperature affect the colour of a star?
Hot –> Cold Blue, white, yellow, orange, red, (black)
What force is pulling inwards on a star?
Gravity
What is pushing outwards in a star?
Fusion Pressure
What is a nebula?
A cloud of dust
How does a nebula turn into a protostar?
Gravity pulls the dust together
How does a protostar get hot?
The gravitational potential energy of the dust is converted to thermal energy
Why isn’t fusion taking palce in the protostar?
It is not hot enough or high enough pressure for fusion to take place
Why does nuclear fusion only occur at very high temperatures and pressures?
The nuclei are both positive so they repel.
What is the next stage after a protostar?
Main sequence star
What is the start doing during the main sequence?
Fusing hydrogen into helium
What two things are balanced while a star is stable?
The gravity inwards is balanced by the fusion pressure outwards
What is the next stage after main sequence? (there are 2 options)
Red Giant or Red Super Giant
Why do some stars form red giants and some form red super giants?
Stars with more mass turn into red super giants whereas stars with less mass turn into red giants
Why does a main sequence star convert into a red giant/ red super giant?
It runs out of hydrogen to fuse together
What do red giants turn into?
White dwarfs
What do white dwarfs do?
Nothing! no fusion, they just cool down
What does a white dwarf turn into and how?
It cools down to eventually form a black dwarf
What happens to a red super giant when it runs out of helium to fuse?
It goes supernova
What is a supernova?
A giant nuclear explosion
If a very large red super giant goes supernova what does it form?
A black hole
What is a black hole?
An object so dense that nothing, including light, can escape from it
If a smaller red super giant goes supernova what does it form?
A nebula and a neutron star