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For the first time, scientists have the calculations and simulations to explain mysterious flashes from the galaxy OJ 287. Roughly twice every 12 years, from 3.5 billion light years away, the light equivalent of 1 trillion suns flashes in the night sky and then fades away over the next few months. It's a phenomenon that astronomers have been documenting since the late 1880s, originating in a galaxy known as OJ 287.

For more than 40 years, astronomers have attributed the oddly regular bursting behavior to be caused by a pair of extremely massive black holes on a collision course. In theory, supermassive binary pairs are expected to be common—but this is the only system where there is clear evidence for one.

"Supermassive binary pairs like these provide a rare opportunity to investigate how galaxies merge and grow over time," says Sean Ressler, a postdoctoral researcher at the Canadian Institute for Theoretical ÌÇÐÄÊÓƵics (CITA).

Ressler led a study in The Astrophysical Journal Letters that presents the first ever simulations of OJ 287. His three co-authors include Luciano Combi, CITA National fellow at Perimeter institute and the University of Guelph, Bart Ripperda at CITA, and Xinyu Li, Tsinghua University.

For the OJ 287 pair, the primary black hole is one of the largest known, at about 18 billion times the mass of Earth's sun. It's surrounded by a disk of gas falling inward toward its event horizon. The secondary black hole, a mere 150 million times the mass of Earth's sun, repeatedly collides with this disk, creating an explosion of light.

It's an explanation that mostly relies on simple "pen and paper" estimates of how the black holes interact with the surrounding gas. Combi notes the team's paper presents the first-ever simulations of OJ 287 as a whole. Unlike previous estimates, their work was able to study how the disk reacts to the repeated collisions, how the ejected gas interacts with the secondary black hole, and how the secondary black hole twists and amplifies magnetic fields that surround the disk to drive outflows.

"These simulations take into account the complicated interaction between extreme gravity, electrodynamics, and fluid dynamics in order to rigorously test whether or not the model can actually explain the observed outbursts," says Combi. "This is the first time the gas (which produces the light) around the binary hole has been simulated all together."

The team has used its simulations to create based on a foundational physical understanding that truly brings the system at the center of OJ 287 to life.

"For years the idea of a smaller mass black hole colliding with the disk of a larger mass black hole has inspired stunning visualizations and artistic renderings, but now we have some compelling animations that are based on more complex calculations," says Ressler.

The simulations generally confirm the idea that the collision of the secondary black hole with the disk can generate enough energy to account for the observed burst of light. The collisions are also seen to modify the structure of the disk, warping it and creating transient spiral patterns that fall inward.

"These calculations should really be treated as a first step towards fully realistic simulations," Ressler says. "This is a step towards a fully coherent picture of the system."