They are massive stars. This is how NASA describe them:
Hypergiant stars are the puffed-up, aging descendants of the most massive class of stars, called “O” stars. The stars are so massive that their cores ultimately collapse under their own weight, triggering incredible explosions called supernovae.
Hypergiants are the largest of the supergiant class.
Larger mass means that the elements that fuse together to produce energy constantly within the core of the star do so much faster due to an abundance of temperature caused by immense pressure/mass, so the lifespan of a hypergiant is generally less than 1-2 million years.
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Sheldon Cooper commented on :
Thanks beth
Anderson commented on :
Hypergiants are the largest of the supergiant class.
Larger mass means that the elements that fuse together to produce energy constantly within the core of the star do so much faster due to an abundance of temperature caused by immense pressure/mass, so the lifespan of a hypergiant is generally less than 1-2 million years.
UY Scuti is the largest example of a hypergiant.