Black holes pepper our universe, but like their name implies, most are invisible — until something happens to change that. That something is often material flowing into the black hole. And in March 2018, one such previously invisible black hole flared to life when a flood of matter fell inward, allowing astronomers to spot and track the event, ultimately mapping out the region close to a black hole in finer detail than ever before.
That work, published January 9 in Nature, was led by Erin Kara of the University of Maryland and NASA’s Goddard Space Flight Center. Kara also presented the results at a press conference the same day at the 233rd meeting of the American Astronomical Society in Seattle. Using NASA’s Neutron star Interior Composition Explorer (NICER) aboard the International Space Station (ISS), the team watched the stellar-mass black hole (designated MAXI J1820+070, or J1820 for short), which flared to life March 11, every day for months. In that time, they used light echoes, which occur when light from near the black hole is absorbed by the accretion disk farther out and then emitted again in a sort of “echo,” to map out the region close to the black hole and watch how that it changed over time.
