How do astronomers measure the mass of the black hole at the center of the Milky Way?
A. By measuring the radius of the black hole’s horizon. B. From the velocities and distances of stars moving around it. C. From the brightness of the radio source Sgr A*. D. From the redshift of stars and gas falling through its horizon. • The curve of enclosed mass versus radius has a flat part, then an upturn at larger radius? What mass causes these? A. All the mass is produced by stars. B. All the mass is produced by a black hole. C. A point mass causes the flat part; stars cause the upturn. D. A point mass causes the flat part; an accretion disk causes the upturn. E. A star causes the flat part; a black hole cause the upturn. Th 2009 Oct 8: The x-rays emitted from Cygnus X-1 come from: A. The main sequence star. B. A neutron star. C. A black hole. D. An accretion disk around the compact object. E. A jet. –> • How do astronomers conclude that a compact object in an x-ray binary is a black hole, as opposed to something else (such as a neutron star)? A. More than 3 solar masses in a
