Question

Draw a labelled H-R diagram. How does it help into estimating the size and mass of a star.

Answer 1

The Hertzsprung–Russell diagram is presented below:

The dwarfs has the least mass and size, and the most massive and big stars are the giants, because the mass is proportional to root of some power (from 1 to 4) of the luminosity. Also, within the main sequence, stars of class 0 are bigger than stars of M class, or hottest stars are the biggest in that area.