Black hole breakthrough reveals wobbling jets spotted by supercomputers
With the help of pioneering supercomputer simulations, scientists have made a tantalising breakthrough to understanding how black holes interact with space-time.
Black holes are known for gobbling particles and light with their colossal gravitational effects, but there is a mysterious material that does manage to escape their maw. Known as “relativistic jets”, they shoot out from black holes across millions of light years.
Given the difficultly of observing and studying black holes, a team of researchers from Northwestern University and Amsterdam University turned to high-powered supercomputers to simulate the actions of these relativistic jets.
“Similar to how water in a bathtub forms a whirlpool as it goes down a drain, the gas and magnetic fields that feed a supermassive black hole swirl to form a rotating disk – a tangled spaghetti of magnetic field lines mixed into a broth of hot gas,” explains Northwestern University, in a rather delicious sounding overview of the research.
“As the black hole consumes this astrophysical soup, it gobbles up the broth but leaves the magnetic spaghetti dangling out of its mouth. This makes the black hole into a kind of launching pad from which energy, in the form of relativistic jets, shoots from the web of twisted magnetic spaghetti.”
The study, published in the Monthly Notices of the Royal Astronomical Society, found that relativistic jets periodically change their direction due to the position of space-time spinning around the black hole.
While previous simulations have tended to align the spinning disk with the black hole’s orientation, the researchers claim most supermassive black holes – such as the one at the centre of our galaxy – have tilted disks, at a different axis to the black hole itself.
Similar to how a spinning top will change its orientation as it spins (a movement known as precession), the spinning disk around a black hole will also ‘wobble’ – changing the direction of its relativistic jets.
To simulate the region surrounding a rapidly spinning black hole requires a massive amount of computational power, hence why it has taken so long for this precession to be discovered. The researchers were able to manage this by conducting the first black hole simulation code accelerated by graphical processing units (GPUs), with the help of the Blue Waters supercomputer. You can see the results on the right side of the below video.
“The high resolution allowed us, for the first time, to ensure that small-scale turbulent disk motions are accurately captured in our models,” said Alexander Tchekhovskoy, assistant professor of physics and astronomy at Northwestern’s Weinberg College of Arts and Sciences.
“To our surprise, these motions turned out to be so strong that they caused the disk to fatten up and the disk precession to stop. This suggests that precession can come about in bursts.”
The results from this study will be critical for further investigations into black holes, as well as phenomena like gravitational waves from neuron star collisions and the engulfing of stars by supermassive black holes. The simulation is also being used to interpret observations from the Event Horizon Telescope (EHT), examining the black hole at the heart of the Milky Way.