New NASA visualization examines the light bending dance of binary black holes

A few orbiting black holes millions of times around the sun’s mass perform a hypnotic pas de deux in a new NASA visualization. The film follows the twisting and redirection of the black holes that emerge from the maelstrom of hot gas, called an accumulation disk.

Viewed from near the track level, each growth disk has a distinctive double hump. But as one goes before the other, the gravity of the black hole in the foreground turns its partner into a rapidly changing series of arcs. These distortions play out as light from both disks navigates the jumbled dust of space and time near the black holes.

“We see two supermassive black holes, a larger one with 200 million solar masses and a smaller companion that weighs half as much,” said Jeremy Schnittman, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. created visualization. “These are the kind of black-hole binary systems where we think both members can maintain growth disks for millions of years.”

The growth discs have different colors, red and blue, to make it easier to find the light sources, but the choice also reflects reality. Warmer gas gives light closer to the blue end of the spectrum, and materials orbiting smaller black holes experience heavier gravitational effects that produce higher temperatures. For these masses, both growth disks will emit most of their light in the UV, with the blue disk being slightly higher.

Visualizations like these help scientists to imagine the fascinating effects of extreme gravity’s funhouse mirror. The new video was duplicated on an earlier one produced by Schnittman showing a lone black hole from different angles.

The growth disks look almost brighter on one side. Gravitational distortion changes the light paths coming from different parts of the disks, producing the skewed image. The rapid movement of gas near the black hole changes the brightness of the disk through a phenomenon called Doppler boosting – an effect of Einstein’s theory of relativity that brightens and turns the side facing the viewer.

The visualization also shows a more subtle phenomenon called relativistic aberration. The black holes appear smaller as they approach the viewer and larger as they move away.

These effects disappear when you see the system from above, but new features appear. Both black holes produce small images of their mates circling around them. If we look closer, it is clear that these images are actually a view. To produce this, the light from the black holes must be redirected by 90 degrees, which means that we observe the black holes simultaneously from two different perspectives.

“A striking aspect of this new visualization is the similar nature of the images produced by gravity lens,” Schnittman explained. “To zoom into every black hole reveals several, increasingly distorted images of his mate.”

Schnittman created the visualization by calculating the path of light rays from the accretion slides as they moved through the skewed space-time around the black holes. On a modern desktop computer, the calculations needed to make the film frames would take about a decade. So Schnittman, along with Goddard computer scientist Brian P. Powell, used the Discover supercomputer at the NASA Center for Climate Simulation. With only 2% of Discover’s 129,000 processors, these calculations took about a day.

Astronomers expect to detect gravitational waves in the not-too-distant future – ripples in space-time – that are produced when two supermassive black holes in a system much like the one depicted by Schnittman spiral together and merge.

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