40-year-old cosmic mystery solved by most accurate black hole simulation ever

6 Jun 2019

The black hole simulation. Image: Sasha Tchekhovskoy/Northwestern University; Matthew Liska/University of Amsterdam

Researchers have constructed a simulation of a black hole so accurate that it has helped solve a 40-year-old cosmic mystery.

Earlier this year, the world saw its first glimpse of the event horizon of a black hole and with it came the promise that whole new discoveries in astrophysics would emerge. Now, an international team has used all of our scientific knowledge to construct the most detailed, highest-resolution simulation of a black hole to date.

In a paper published to Monthly Notices of the Royal Astronomical Society, the team of computational astrophysicists from Northwestern University, the University of Amsterdam and the University of Oxford were able to solve a pressing 40-year-old mystery.

In 1975, Nobel Prize-winning physicist John Bardeen and astrophysicist Jacobus Petterson argued that a spinning black hole would cause the inner region of a tilted accretion disc – the matter that orbits and falls into a black hole – to align with the hole’s equatorial plane.

For years, our limited ability to observe and better understand black holes had left their theory unproven. However, the team’s simulation found that while the outer region of an accretion disc remains tilted, the disc’s inner region aligns with the black hole.

Haunted no more

In the simulation, the team thinned the accretion disc to an unprecedented degree while adding the magnetised turbulence that causes the disc to accrete. Until now, simulations could only run a simplified test by just approximating the effects of turbulence.

“This groundbreaking discovery of Bardeen-Petterson alignment brings closure to a problem that has haunted the astrophysics community for more than four decades,” said Northwestern’s Alexander Tchekhovskoy, who co-led the research.

“These details around the black hole may seem small, but they enormously impact what happens in the galaxy as a whole. They control how fast the black holes spin and, as a result, what effect black holes have on their entire galaxies.”

Another interesting discovery made by the team was that despite incredibly thin accretion discs, the black hole simulation still emitted powerful jets of particles and radiation.

Looking to the future, the team said that with this problem now solved, it will open the door for future researchers to generate their own simulations, which could lead to further discoveries regarding luminous accretion discs.

Colm Gorey was a senior journalist with Silicon Republic