Zachariah Etienne, assistant professor of mathematics at WVU, recently received funding to collaborate on a project with theoretical astrophysicists at NASA Goddard Space Flight Center. The three-year project will study black holes and produce theoretical models of what astronomers may observe using NASA telescopes.
Black holes are usually thought of as the result of a very massive star that has died. However, black holes millions of times more massive than such stars are thought to exist at the cores of all galaxies, including the Milky Way. How such supermassive black holes gained so much mass remains a mystery. One popular idea is that they were built up through “swallowing up” nearby matter and galaxy collisions.
When galaxies collide, their cores eventually merge. Deep inside the common core, the supermassive black holes’ gravitational fields interact, and gravitational waves carry away the very energy that keeps the black holes apart. As a result, they black holes spiral toward one another and merge.
Researchers want to learn more about not only the nature of gravitational waves from orbiting supermassive black holes, but also their corresponding light signatures.
These gravitational waves could potentially be detected through the North American Nanohertz Observatory for Gravitational Waves.
“The Observatory, along with its international counterparts, represent our best hope for observing gravitational waves from orbiting supermassive black holes that are extremely far away,” Etienne said. “If both light and gravitational waves can be viewed simultaneously, it stands to greatly advance our understanding of how these holes and their galaxies develop.”
Etienne will be working with NASA Goddard research astrophysicist Jeremy Schnittman, research associate Bernard Kelly, John Baker, who is the primary investigator on the project, and Bruno Giacomazzo, a collaborator from Italy.
WVU’s high performance computer system, Spruce Knob, as well as NASA and National Science Foundation supercomputers, will be critical for performing the simulations necessary for these theoretical models. Etienne has spent most of the last decade developing a core piece of software used to produce these simulations.
The software, IllinoisGRMHD, creates models of magnetized fluid flows in and around objects with very strong gravitational fields, such as black holes.
Models created with the software will help researchers understand how magnetized fluid flows behave around objects with incredibly strong gravitational fields. They can then use model data to better understand how light is created by black holes.
The simulations that Etienne will be performing will help share insight into how that light is emitted, as well as give scientists a better understanding of the mechanisms that are generating the incredibly bright light that can be observed to the farthest stretches of the universe.
“We can see light coming from matter falling into black holes from all the way across the universe,” Etienne said. “In fact, some of the most distant objects seen in the universe, probably all of them, are due to the phenomena of magnetic fields and magnetic fluid flows around these very, very massive black holes.”
Supermassive black holes usually have a mass that is somewhere between 1 million and 1 billion times the mass of our sun.
“The supermassive black hole at the center of our galaxy is roughly 4.3 million times the mass of our sun,” Etienne said.
The black holes that can be observed in the universe are very diverse. Some supermassive black holes are so active that they disrupt the dynamics of the galaxy that they inhibit.
The one at the center of the Milky Way, however, is calm compared to others, called active galactic nuclei.
“These are black holes that are rambunctious, they’re causing all sorts of havoc in their host galaxies. Although our black hole is relatively quiet and well-behaved, you don’t want to get too close to it or fall into it, but it’s not going to destroy the Earth or things nearby.”
Funding comes from NASA’s Astrophysics Theory Program and will support the project for three years. Etienne is currently working on other projects with the Department of Physics and Astronomy.