BBC: To estimate the mass of a black hole, astronomers look at the movement of the stars or plasma around it. But the method is time-consuming and inaccurate because of the random motions of the bodies being measured. Timothy Davis of the European Southern Observatory and his colleagues have developed a new technique that uses images of microwave radiation emitted by cold clouds of carbon monoxide gas. Because the gas is cold, the random, thermal motions are less vigorous, resulting in less blurring of the images. And because the images are in the microwave part of the spectrum, they are at higher resolution than previous measurements in the radio. Davis’s team used California’s Combined Array for Research in Millimeter-wave Astronomy to map the movements of particles at various distances from a black hole in NGC 4526. The researchers calculated the black hole to have a mass 450 million times the mass of our sun. Davis believes that the next generation of microwave telescopes will provide even clearer measurements and will significantly reduce the time it takes to make similar calculations.