Hunting a black hole Observations of the light from a certain star indicate that it is part of a binary (two-star) system: This visible star has orbital speed v = 270 km/s, orbital period T = 18.1 days, and approximate mass m1 6.9Ms, where Ms is the Sun's mass, 1.99 x 1030 , kg: Assume that the visible star and its companion star; which is dark and unseen, are both in circular orbits (see the figure). Find the ratio of the approximate mass mz of the dark star to Ms: Number Units Nounits
