Question

How are g-r values related to the star's temperature? Give a short explanation.

Answer 1

The g-r value is one way to find the colour but astronomer have other option as well. Astronomer should also use u-r, r-i etc to measure colour.

When a astronomer talk about the color of the star then he or she is talking about the magnitude difference measurement g-r, u-i etc he or she would not talk about the colour but for eg . he or she would say something like' the star has a colour of g-r value 1.5'

As the temperature of star increase that means total radiated energy also increases, and the peak of curve moves to shorter wavelength i. e. Light is pushed further and further towards the blue end of the spectrum corresponding to small value of color index. (more blue object)

Larger the colour index the more red(temperature decrease) the object is.