What happens inside a black hole stays inside a black hole, but what happens inside a black hole’s “sphere of influence” – the innermost region of a galaxy where a black hole’s gravity is the dominant force – is of intense interest to astronomers and can help determine the mass of a black hole as well as its impact on its galactic neighborhood. New observations with the Atacama Large Millimeter/submillimeter Array (ALMA) provide an unprecedented close-up view of a swirling disk of cold interstellar gas rotating around a supermassive black hole. This disk lies at the center of NGC 3258, a massive elliptical galaxy about 100 million light-years from Earth. Based on these observations, a team led by astronomers from Texas A&M University and the University of California, Irvine, have determined that this black hole weighs a staggering 2.25 billion solar masses, the most massive black hole measured with ALMA to date.

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