Collapses (slowly at first).
If enough dust, the particles form solid object.
If even more dust, the gravity of the object causes high pressure at the centre. Centre becomes molten (this is why all large planetary bodies are spherical - the core melts so the upper surface settles to a uniform shape).
If the object is REALLY big, the pressure causes fusion of hydrogen into helium.
Fusion releases energy.
Energy = heat and light
Energy irradiated over life of star.
Towards end of life, star expands. This is because the core has lost a lot of mass by this time, so the outer layers undergo less gravitational effects.
Core starts to burn out - not enough energy released to keep outer layers stable, centre of star collapses, layers fall inwards, impact causes mass ejection of elements.
This happens a few times.
Eventually only the core us left.
Core now very dense.
Neutron star formed. End.
If star not large enough, it just burns out, no explosions, nothing special. Becomes a brown dwarf. Eventually dies. Presumably becomes a large dead rock of heavy metal in space.
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Red Giant is the part where the star expands.
It goes something like this:
- Dust cloud
- Large object (if large enough, fusion begins)
And then, depending on the size of the star:
- Expands to ted giant
- Partially collapses (outer layers ejected, known as a planetary nebula)
- Burns out into white dwarf and simply fades away, OR
- Expands to red giant
- Collapses (nova = mini explosions releasing outer layers, then supernova = whole thing properly goes boom)
- Tiny dense neutron core remains ( = neutron star, or black hole if the remaining core has enough mass)