This double star system is observed to complete one revolution in 35 yr. What is M2?(For comparison, the distance from the sun toEarth is about 1.5 × 1011 m, and the mass ofthe Sun is about 2 × 1030kg.) This methodis often used to determine the masses of stars.The mass of a star largely determines manyof the other properties of a star, which is whyastrophysicists need a method for measuringthe mass.