The supermassive black holes at the center of galaxies can become some of the most powerful objects in the universe once they go into a feeding frenzy.

Some launch jets of plasma millions of light-years from the galaxy but since not all of them do that, researchers from Berkley and the Hebrew University of Jerusalem carried out simulations to understand this difference in behavior.

They looked at how the magnetic field from the black hole would interact with the material in the inner region of galaxies, and worked out how some can punch out of their host galaxy and into intergalactic space, and others can even reach the edge of the galaxy.

“Whereas it was rather easy to reproduce the stable jets in simulations, it turned out to be an extreme challenge to explain what causes the jets to fall apart,” said Berkeley's Alexander Tchekhovskoy, who led the project, in a statement.

“To explain why some jets are unstable, researchers had to resort to explanations such as red giant stars in the jets’ path loading the jets with too much gas and making them heavy and unstable so that the jets fall apart.”

To solve this problem, which has puzzled scientists for 40 years, the simulation had to be 3D, consider the whole system, launch jets consistent with a rotating black hole, and include the magnetic field of the system. And the key to solving the mystery was the magnetic instabilities in the jets.

In the paper, available online and accepted for publication in the Monthly Notices of the Royal Astronomical Society, the researchers show that if the jet is not strong enough to penetrate the surrounding material, then the magnetic field keeps the jet in a narrow volume, which either breaks it apart or bends it. A powerful jet remains undisturbed and quickly stretches beyond the galaxy.

“We have shown that a jet can fall apart without any external perturbation, just because of the physics of the jet,“ Tchekhovskoy added.

The interactions between the black holes’ jets and material from the galaxy are also responsible for a feedback mechanism that can regulate how big black holes get (the biggest so far is 21 billion solar masses) but also generates galaxy-wide winds that heats up the gas abruptly, quenching star formation.

Although jets last only 10 to 100 million years, their impact can play a pivotal role in the life of galaxies and understanding them provides an important new clue on galaxy evolution.