Newtons laws of motion and gravity allow astronomers to determine the?

Question

a. luminosity of stars.

b. masses of binary stars.

c. masses of individual stars.

d. stellar parallax.

Answer 1

It's not 'a' or 'd'. I'd go for 'b' as the centre of rotation of two masses is determined by the common centre of gravity - which will be closer to the more massive star. I don't see how it can give you the absolute masses of binary stars - only the relative masses.

Answer 2

b.