Life Cycle of a Star
Black dwarf
A dead star that is no longer hot nor bright
Main sequence star
A star during the main part of its life cycle, where it is using hydrogen as a fuel.
White dwarf
A star that has collapsed from the red giant stage to become much hotter and denser than it was.
Red giant
A star that has expanded and cooled, resulting in it becoming red. It has used up all the hydrogen in its core and is now using helium as a fuel.
Red supergiant
A star that has used up all the hydrogen, is using helium as fuel, creates heavy elements in its core (up to iron), and has a mass much higher than the Sun.
Nebula
The concentration of dust clouds and gas in space that forms a star.
Protostar
The condensing and heating of hydrogen atoms and dust before the star is born. There is no nuclear fusion yet.
Neutron star
The core of a red supergiant that has collapsed but can can be seen.
Black hole
The core of a red supergiant that has collapsed. These are formed if the remaining core has a mass more than three or four times the mass of the Sun. It is so dense that light can't escape it.
Nuclear Fusion
When nuclei of hydrogen atoms join together to form helium and they release energy in the process.
Supernova
An explosion produced when the core of a red supergiant collapses.
Planetary nebula
The stage of a dying red giant star where all its gases have drifted away due to its weak gravity
