Astronomers have made precise measurements of the mass of a supermassive black hole.
Aaron Barth of the University of California in Irvine focused the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile on the black hole at the heart of NGC 1332, a galaxy that is roughly 22 million parsecs (73 million light years) away. ALMA's high-resolution images revealed carbon monoxide gas orbiting just outside the black hole. By measuring the velocity of the gas, the team found the black hole to be 664 million times the mass of the Sun, with an uncertainty of roughly 10%.
The technique improves on less-direct measurement methods.
Astrophys. J. Lett. in the press; preprint at http://arxiv.org/abs/1605.01346 (2016)