Question

Everything we know about stars comes from studying their _____.

mass
color
temperature
radiation/light
age

Answer 1

Light / Radiation. The light radiation defines its color. Thermal radiation for its temperature and the overall appearance of the wavelengths the star emits gives off the info from where astronomers and scientist are able to build up knowledge on the age and current state of the stars

Answer 2

Everything we know about stars comes from studying their radiation/light. By measuring the wavelength or frequency of light coming from objects in the universe, we can learn something about their nature.  Starts emit a range of wavelengths. The frequency of light is directly related to its color, so it follows that stars have different colors because they have different peak wavelengths of light.