Astronomers have measured the “weight” of a massive black hole with unprecedented precision.
Discovery Magazine reports that the supermassive black hole situated at the center of galaxy NGC 1332 is 660 million times the mass of the Sun. Astronomers calculated the mass of the black hole using data from the Atacama Large Millimeter/submillimeter Array (ALMA) located in Chile.
Rather than imaging the black hole directly, ALMA gathered measurements of the gases trapped within the black hole’s gravitational well.
“To calculate the mass of a black hole in a galaxy’s center, we need to measure the speed of something orbiting around it,” Aaron Barth of the University of California said. “For a precise measurement, we need to zoom in to the very center of a galaxy where the black hole’s gravitational pull is the dominant force.”
Because black holes allow nothing – not even light – to escape their gravitational pull, scientists must observe them indirectly. Measurements can be taken, for example, of the hot gas emissions emanating from a black hole’s accretion disk, or from the extent to which a black hole warps space-time to create a light-bending effect.
In the case of ALMA’s recent observation, nearby cold gases were detected and their speed and distance from the black hole were used to calculate the black hole’s mass with great precision.
The elliptical galaxy containing the monster black hole lies about 75 million light years from Earth, and the black hole at its center has built up a swirling gas disk 1600 light years across. ALMA’s ability to observe the disk’s radio emissions allows scientists to measure structures as small as 16 light years across within the disk.
The black hole’s “sphere of influence” stretches 80 light years into space from its core, and the gases in the spinning disk reach speeds of 300 miles per second.
“ALMA is a fantastic new tool for carrying out these observations,” Barth said.