How can light teach us information about the stars and/or about galaxies?

Explained

Explanation:

Light from the distance objects can be used to find the luminosity of the object. Once, Luminosity is known that is the energy emitted by the starts are known.

Scientist can now find out the temperature of the stars because Hot objects emit more of their light of short wavelength and cold objects emit more of their light of longer wavelength. Therefore the difference in temperature of the stars can be known.