A Black Hole I? You’ve just discovered a new X-ray binary, which we will call Hyp-X1 ("Hyp" for hypothetical). The system Hyp-X1 contains a bright, B2 main-sequence star orbiting an unseen companion. The separation of the stars is estimated to be 20 million kilometers, and the orbital period of the visible star is 4 days. a. Use Newton’s version of Kepler’s third law to calculate the sum of the masses of the two stars in the system. (Hint: See Mathematical Insight 15.4.) Give your answer in both kilograms and solar masses (MSun = 2.0 * 1030 kg). b. Determine the mass of the unseen companion. Is it a neutron star or a black hole? Explain. (Hint: A B2 mainsequence star has a mass of about 10MSun.)