in the constellation Coma Berenices
1 billion to 9 billion times the mass of the Sun
Diameter at least equal to the diameter of Neptune's orbit around the Sun
The black hole at the center of the elliptical galaxy NGC 4061 may be the most massive yet discovered. The upper limit of current estimates place it at nine billion times the mass of the Sun, which would make it three times more massive than the black hole in M87, the current champion. At that mass, the black hole would be more than twice the diameter of our solar system, including the Kuiper Belt -- the disk of icy comets that extends far beyond the realm of the planets.
There is a wide range in the estimates, though; the minimum puts it at just one billion solar masses. That’s a monster black hole by any measure, but would not give it first-place honors.
Astronomers have used two related methods to estimate the black hole's mass.
In one, they have measured the motions of stars in the galaxy’s inner regions. Stars closer to the center of the galaxy move substantially faster than those a little farther out, indicating that the stars orbit a massive, compact object. From the difference in speeds at different distances, astronomers calculate that the black hole's mass is about one billion times that of the Sun.
The other method measures the motions of gas around the black hole. It, too, looks at the speed at different distances from the black hole. With this technique, astronomers have estimated the mass of the black hole at either two billion times the mass of the Sun, or three to nine billion times the mass of the Sun. The difference is caused by different sets of observations and different models of how the gas is moving.
More-precise observations with future ground- or space-based observatories should help resolve the issue and tell us whether the black hole at the center of the NGC 4061 is the heaviest yet discovered.
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This document was last modified: November 19, 2009.