From nebula to protostar to main sequence, the two different endings depending on mass, and where the chemical elements were made. Physics only content.
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1.What is a nebula?
A cloud of dust and gas in space, which is where stars begin to form.
2.What causes a nebula to start forming a star?
Gravitational attraction pulls the dust and gas together.
3.What is a protostar?
The hot dense body formed as a nebula collapses, before nuclear fusion has begun.
4.Why does a protostar get hotter as it collapses?
The particles gain kinetic energy as gravity pulls them inwards, raising the temperature.
5.What starts when a protostar becomes hot and dense enough?
Nuclear fusion of hydrogen nuclei into helium.
6.What is the main sequence stage?
The long stable period in which a star fuses hydrogen into helium.
7.Why is a main sequence star stable?
The force of gravity pulling inwards is balanced by the outward pressure from the energy released by fusion.
8.What is our Sun currently doing?
It is a main sequence star, fusing hydrogen into helium.
9.What happens when a star runs out of hydrogen?
Fusion slows, gravity is no longer balanced, and the star expands and cools to become a red giant or red supergiant.
10.Which stars become red giants?
Stars about the size of our Sun.
11.Which stars become red supergiants?
Stars much more massive than our Sun.
12.What happens to a star the size of the Sun after the red giant stage?
It contracts to become a white dwarf, which then cools to a black dwarf.
13.What is a white dwarf?
The hot dense core left behind when a red giant sheds its outer layers.
14.What is a black dwarf?
A white dwarf that has cooled so much that it no longer emits visible light.
15.What happens to a red supergiant?
It explodes as a supernova.
16.What is left after a supernova?
Either a neutron star, or a black hole if the star was massive enough.
17.What is a black hole?
An object so dense that its gravitational field is strong enough to prevent even light escaping.
18.State the full sequence for a star the size of the Sun.
Nebula, protostar, main sequence star, red giant, white dwarf, black dwarf.
19.State the full sequence for a star much larger than the Sun.
Nebula, protostar, main sequence star, red supergiant, supernova, then a neutron star or a black hole.
20.Which elements are produced by fusion in stars?
Elements up to and including iron.
21.Where are elements heavier than iron produced?
In the explosion of a supernova.
22.How are those elements spread through the universe?
A supernova distributes them across space, where they later form new stars and planets.
23.What does this tell us about the atoms in our bodies?
They were made inside stars and scattered by supernovae, long before the solar system formed.
24.Why do more massive stars have shorter lives?
They fuse their hydrogen at a far greater rate, so their fuel is used up much more quickly.
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