Im confident that my teacher is right and its age. I stupidly put luminosity because i kept on second guessing my self on absolute magnitude being mass and then it would be luminosity was constant because as the star got bigger it emmited more energyHave we agreed on anything for the Hertsprung-Russel diagram? I think I said age, because colour and luminosity are the values on the axis, so there's variation and there's stars with the same colour but different luminosity, so their surface area, and resultantly mass, must be different?