Question

Why are supergiant so bright?

Answer 1

because the core tempature gets much hotter.

Step-by-step explanation:

so supergiants can fuse elements heavier than hydrogen and helium. But to support their tremendous mass, supergiants burn up their fuel much more quickly.

Answer 2

Because supergiants are so massive, the core temperature gets much hotter than in giants, so supergiants can fuse elements heavier than hydrogen and helium. But to support their tremendous mass, supergiants burn up their fuel much more quickly.