Question

Stars are very hot and bright .why?

Answer 1

The main factor determining the brightness and surface temperature of an average "main sequence" star is the stellar mass.In general, stars more massive than the Sun are hotter and brighter and less massive stars are cooler and less bright.

Answer 2

the main factors determine the brightness and surface temperature of an average main sequence star is the steller mass. In general stars more massive than the sun are hotter and brighter and less massive stars are cooler and less bright