“To measure the mass and spin of the black hole, we need to know exactly where this gas is before it falls into the black hole,” Alston says. The team could then use that information to calculate the black hole’s mass and spin, two properties that do not fluctuate on human timescales. The light echoes captured from IRAS 13224-3809 allowed Alston and his team to determine the precise geometry of the material surrounding the black hole, including the dimensions of its dynamic x-ray corona, which powers those echoes. “Instead, it uses light echoes within the object to tell us about structures, even very small and very far away ones.” “Reverberation mapping doesn't rely on spatial resolution at all,” says Georgia State University’s Misty Bentz, who uses the same technique to study distant black holes. And, unlike the process used by the Event Horizon Telescope to assemble an image of a nearby black hole, reverberation mapping can be used to study objects that are far, far away and probe regions even closer to the event horizon.

Alston compares the process to echolocation, in which animals such as bats bounce sound off objects to help them navigate in flight. This technique, called reverberation mapping, helped the scientists probe the gassy material around the black hole. “We can measure the echo-this time delay-which we call a reverberation.” “This extra path length causes a time delay between the x-rays that were produced originally in the corona,” Alston explains. Some of the emitted x-rays head directly into the cosmos, but others slam into the accretion disk and take a little longer to exit the bruiser’s immediate environment. An Earth-orbiting telescope that studies the cosmos in x-rays, XMM-Newton stared at the distant galaxy over the course of 16 orbits-totaling more than 550 hours-between 20.įrom those many hours’ worth of data, Alston and his colleagues assembled a map of the supermassive black hole’s x-ray corona and its accretion disk, a ring of swirling matter that’s just outside the event horizon. To do that, Alston and his colleagues studied IRAS 13224-3809 using the European Space Agency’s XMM-Newton spacecraft. Alston and his colleagues chose to study this particular galaxy because they wanted a dynamic, fluctuating source that could help them nail down specific properties of the central supermassive black hole. Echo mappingĭespite the innocuous name, IRAS 13224-3809 is one of the most exciting galaxies in the x-ray sky: It is an active galaxy, meaning that its innermost region shines more brightly than can be explained by stars alone, and its x-ray brightness fluctuates by a factor of 50, sometimes over just a few hours. “Understanding the spin distribution of black holes in many galaxies tells us about how we go from the early universe to the population we see today,” Alston says.

If similar measurements can be made for a larger population of nearby supermassive black holes, they could help scientists learn more about how galaxies grow. The new measurements of IRAS 13224-3809’s black hole helped scientists pin down its mass and spin, properties that can reveal vital clues about the black hole’s evolution. It’s a much more precise measurement than even the Event Horizon Telescope, which produced last year’s black hole picture, could make for an object so far away. “Black holes don’t give off any light themselves, so the only way we can study this is by watching what matter does as it falls onto it,” says the University of Cambridge’s William Alston, whose team reports the observations today in the journal Nature Astronomy. Learn about the types of black holes, how they form, and how scientists discovered these invisible, yet extraordinary objects in our universe. At the center of our galaxy, a supermassive black hole churns.

Sending a satellite into a black hole