How it works
Every star is born in a nebula, grows from a protostar and spends most of its life as a main sequence star. What comes next depends on its mass, so the diagram splits into two paths.
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A Sun-like star
When its hydrogen runs low it swells into a red giant, a few hundred times bigger. The outer layers drift off as a planetary nebula, and the core is left as a white dwarf about the size of Earth.
A massive star
A star of more than about seven times the Sun's mass swells into a red supergiant. Its core collapses and the star explodes as a supernova, leaving a neutron star or, from the heaviest stars, a black hole.
- The sizes only show which stage is bigger than the last; a real red giant would dwarf the whole drawing.
Questions and answers
What are the stages of the life cycle of a star?
Nebula, protostar and main sequence star for every star. A Sun-like star then becomes a red giant, a planetary nebula and a white dwarf; a massive star a red supergiant, a supernova, and a neutron star or a black hole.
What stage of its life cycle is the Sun in?
The main sequence, fusing hydrogen into helium in its core. It will later swell into a red giant and end as a white dwarf.
What decides how a star ends?
Its mass. A star of up to about seven times the Sun's mass ends as a white dwarf; a heavier one explodes as a supernova and leaves a neutron star or a black hole.