Black holes are often misunderstood as mere dark and mysterious voids akin to Alice in Wonderland’s perplexing rabbit hole. In reality, black holes are the densest objects in the universe, exerting tremendous gravitational pull that gathers the surrounding fabric of space and time, generating massive disks of matter that whirl toward the black hole before crossing the point of no return.
In recent years, as astronomers have been able to focus more telescopes on the sky for extended periods, they have captured a surprising range of black hole behavior. Erin Kara, an associate professor of physics at MIT, states, "It used to be that we didn’t have eyes on systems all the time. Now we’re seeing that they can turn on and off at rates that are much faster than we ever thought possible."
Kara and her team at MIT’s Kavli Institute for Astrophysics and Space Research are at the forefront of black hole physics. They utilize data from both ground and space telescopes to study the properties of black holes, especially supermassive black holes, which are the ultradense giants at the centers of galaxies. Supermassive black holes are the engines of galaxy formation, and Kara aims to connect the extreme physics of black holes with the formation of galaxies like our Milky Way. "It’s amazing that we as humans can know anything about what’s happening billions of light years away," Kara says.
Born and raised in Bethlehem, Pennsylvania, as the youngest of four, Kara initially pursued a premed track at Barnard College of Columbia University. However, after taking an introductory physics class, she became captivated by the subject's fundamental descriptions of the physical world, from quantum to cosmic scales. This led her to switch from premed to physics.
During her time at Cambridge University, Kara completed her PhD on black hole X-ray reverberation. Her thesis advisor, Andy Fabian, discovered curious time delays in signals from a black hole, interpreted as X-ray echoes. This provided the first evidence of X-ray echoes around a black hole, resolving a debate in the field regarding the radiation source. Kara advanced the study of X-ray reverberation to map regions around black holes.
After earning her PhD, Kara returned to the U.S. for postdoctoral work at the University of Maryland and NASA. She initially intended to work on the Hitomi satellite project, which ultimately failed after 40 days. However, the data from Hitomi confirmed the soundness of its detector, now integral to the X-ray Imaging and Spectroscopy Mission (XRISM), which is successfully collecting data since its launch in 2023. Today, Kara leads a science group analyzing X-ray signals from supermassive black holes.
Kara also plans to explore data from future observatories, including the Ultraviolet Transient Astronomy Satellite (ULTRASAT) and the Laser Interferometer Space Antenna (LISA). In a unique collaboration, she recently converted a black hole’s X-ray echoes into audible sound, merging science with art. "One of the reasons I love black holes is that they are very extreme, feel very sci-fi crazy, and physics breaks down around them. Yet they are foundational to our existence," Kara reflects.
Blogger's Review: Erin Kara's research not only pioneers new directions in black hole physics but also showcases the fusion of science and art. By transforming black hole X-ray echoes into sound, she offers a novel way to understand the universe. The exploration of black holes represents not just scientific inquiry, but humanity's endless quest for the unknown.