- giant star are 10 to 100 times as big as the Sun, and 100 to 1000 times as bright.
- red giant are stars that have swollen 10 to 100 times their size, as they reach the last stages of their life and their outer gas layers cool and expand.
Size of compassion between our sun and red giant star.
- giant stars have burnt all their hydrogen, and so burn helium, fusing (joining) helium atoms to make carbon.
- the biggest stars continue to swell after they become red giants – they then glow onto supergiant.
- supergiant stars are up to 500 times as big as the Sun, with absolute magnitudes of -5 to -10 (see star brightness).
- pressure in the heart of a supergiant is enough to fuse carbon atoms together to make iron.
- all the iron in the universe was made in the heart of supergiant stars.
- there is a limit to the brightness of supergiant, so they can be used as distance markers by comparing how bright they look to how bright they are. (see distance)
- supergiant stars eventually collapse and explode as supernovae.