Reed Alum Reveals First-Ever Black Hole Image
This Wednesday, April 10, researchers at Harvard University, directed by Harvard Professor of Astrophysics and Reed alum Sheperd Doeleman ‘86, with algorithms written by Dr. Katie Bouman, unveiled the first-ever “photograph” of a black hole.
The image is the end result of two years of computer analysis of radio waves collected in the span of only 10 days in a nearly worldwide network of antennas known as the Event Horizon Telescope. The black hole imaged was the supermassive black hole at the center of the Messier 87 galaxy. Its mass is billions of times that of our sun.
Supermassive black holes are the most massive objects in the universe, and are distinct from the much smaller stellar black holes. While stellar black holes are the remnants of giant stars that have died in supernovae and collapsed, the origins of the supermassive black holes found at the center of many galaxies are much more mysterious. Some astrophysicists believe that they form when new galaxies do, from collapsing clouds of dust and gas. Others think that they originate as stellar black holes consume more and more matter over time growing to an enormous size, or are the product of the collisions of multiple stellar black holes.
The mystery of black holes lies in their very definition. Black holes are so dense that not even light can escape, which makes them difficult to visualize. Seemingly conversely, supermassive black holes also form quasars, the brightest objects in the universe. As matter is pulled towards a supermassive black hole, it speeds up, which heats up the matter to incredibly high temperatures. The thermal energy released as photons spans the x-ray and visible as well as the radio spectrum.
Since the 1950s, physicists have been aware of the incongruous amount of radio waves emanating from “seemingly peaceful” galaxies. Almost half a century earlier, Einstein’s theory of relativity predicted that spacetime could warp into black holes.
The idea behind Doeleman’s project was both simple yet ridiculously complicated: they were going to combine the radio wave imaging from eight different telescopes on four different continents and run the resulting 10 days worth of data through various computer programs to produce the first ever image of a black hole. Two years after the imaging itself took place, the computer work is finished and the world has its first-ever image of a black hole.
The ringlike structure of the black hole image follows with what researchers predicted: the bright outer ring is the superheated matter being pulled into the black hole. As expected, the inner part of the ring — close to the black hole itself — is dark, because no light can escape the gravity of the black hole past a certain point.
Dr. Katie Bouman was a PhD student in computer science and artificial intelligence at Massachusetts Institute of Technology (MIT) when she developed the groundbreaking algorithms that allowed the team to turn the telescope radio wave data into the final image. “We didn't want to just develop one algorithm,” Bouman said in an interview with CNN. “We wanted to develop many different algorithms that all have different assumptions built into them. If all of them recover the same general structure, then that builds your confidence.” Her work, in addition to that of Doeleman and others, was crucial to this groundbreaking discovery.