In Interstellar, a recent sci-fi motion picture featuring some of today’s biggest stars, astronauts ride a starship as it propels through a black hole in space. This Hollywood version of star travel shines a new spotlight on the study of black holes and Einstein’s Theory of General Relativity. Although the science may be unfamiliar to movie watchers, new faculty member Scott Noble, assistant professor of physics, has investigated the phenomena since his days as a graduate student in the early 2000s.
“There was a wealth of astronomical data coming out at that time, and we were learning more and more about black holes,” he said. “I was interested in simulations with black holes in gas.”
His student research focused on the collapse of neutron stars into black holes. In 2013, as a research scientist at the Rochester Institute of Technology, he collaborated with astronomers from NASA and Johns Hopkins University to study how black holes produce light.
“Black holes contribute to the evolution of a galaxy by altering the orbits of stars, injecting momentum, energy and heat,” Noble said. “Black holes can trigger or quench star formation, and that changes the demographics of a galaxy.”
His expertise in solving hydrodynamic equations contributed to the joint study on the nature of matter around a black hole and how those findings can help astronomers better understand the object’s properties. Noble designed a computer simulation that solves the magnetohydrodynamic equations to represent the gas flow and magnetic field interactions in an area around the black holes known as the accretion disk.
“We make the very reasonable approximation that the gas in the disk is perfectly conducting, which allows us to derive the electric field directly from the magnetic field,” he said. “The set of fluid and magnetic equations is then solved using supercomputers, or collections of thousands of central processing units at once.”
Noble monitored how temperature, density and speed of gas increased along with the magnetic field strength closer to the black hole. His findings showed a raging foam that continuously circles the black hole at lightning speed. With Noble’s data, the team of astrophysicists used tools for tracking how X-rays move through a black hole’s accretion disk and discovered new information about a disk’s appearance in X-rays. The study was published in The Astrophysical Journal.
“Black holes are important because they tell us not only about Einstein’s theory of gravity (his Theory of General Relativity), but also how matter behaves in such intense gravity,” Noble said. “Physics is known well on a microscopic scale — the strong force, weak force and electromagnetic forces are all intimately tied. However, their connection to the fourth force, gravity, is still unknown. Einstein’s Theory of General Relativity is the best theory that describes gravity, but it hasn’t been tested in the strong field dynamical regime, such as near a black hole.”
Noble’s team of students and collaborators will continue research on black hole accretion disks, but he also hopes to improve the numeric predictions of light emitted from gas right before it falls into black holes. His work will advance the codes that more accurately predict the electromagnetic signatures of black holes, a project requiring more sophisticated simulations while factoring in radiation coupled to the magnetohydrodynamics.
“We want to understand what happens to the gas around these black holes,” he said. “Then, we’ll be able to identify these sources with light by using predictions we’ve made. We can extract the physics and test Einstein’s theory to see if he was right all along.”