In the constellation Centaurus
40,000 times the mass of the Sun
Diameter 150,000 miles (240,000 km), about two-thirds of the distance from Earth to the Moon
Measuring the motions of stars
Because a black hole is both massive and compact, it exerts a strong gravitational pull on the material around it. Astronomers can deduce the presence of a supermassive black hole in the core of a galaxy by measuring the velocities of stars that orbit the black hole. A more-massive black hole will accelerate nearby stars to greater speeds, so the velocities of stars can reveal not only the presence of a black hole, but its mass as well.
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This document was last modified: November 11, 2011.