Question

why are blue stars hot and red stars cold​

Answer 1

Answer:

The surface temperature of Eta Carinae is 40,000 Kelvin, and it shines with much of its radiation in the ultraviolet spectrum. ... So, remember, blue stars are blue because of the temperature of their surface. And they're so hot because blue stars are much more massive than cooler stars like our Sun.

Red stars are cooler. They are red because they emit red light, which is lower in energy than blue light. Energy in turn, is proportional to temperature, which means that higher energy corresponds to higher temperatures.

Answer 2

Answer:

because in blue stars neculear reaction are taking place but in red the are about to finish or gases are not enough to generate more heat just like our gas stove gives blue light when complete combustion take place and coal give red