A radio view into a black hole’s backyard

By definition, black holes themselves remain shut off from direct observation. But astronomers have been able to precisely image the sphere of influence of a black hole – the area in which its gravity is the dominant force. In the case of a supermassive black hole in the interior of a galaxy, this area can be up to 500 light-years across. For comparison, the closest star to the Sun is a good four light-years away.

This imaging was done by the Atacama Large Millimeter/submillimeter Array (ALMA...