Answer:
To determine the brightness of the stars.
Explanation:
it is useful for scientists to know the temperature of stars far away from the earth because the scientists want to determine the brightness of the stars. Those stars which are red in colour have low temperature as compared to those starts which have blue colour. This blue colour means that the star has very high temperature so in that way the scientists find out that which star is very hot and which is star is less hotter.
