January 12, 2011 - MSNBC
Astronomers say they've come up with the definitive estimate for the mass and size of the biggest black hole in our celestial neighborhood, using a method that can now be applied to even bigger monsters beyond.
...
"That had a large uncertainty," Gebhardt told me. Today, Gebhardt and his colleagues announced a new estimate that's based on high-accuracy observations from the Gemini Observatory in Hawaii as well as the McDonald Observatory. The bottom line: M87's black hole is equal to 6.6 billion solar masses, plus or minus 400 million solar masses.
...