NASA/JPL-Caltech
Off World

Astronomers Find Jets of Gas May Regulate Black Hole Growth

The strength of the jets may be decided by the twisting magnetic field of the black hole.

Black Hole Fireworks

Astronomers from the University of California, Berkeley have formulated a simulation that would explain why some supermassive black holes shoot out jets of ionized gas. Some of these are strong enough to slice through their galaxy in the form of bright streaks of light; others are just duds. Reasons why some do and some don’t, has been a mystery for a while. The unpredictability of these jets has not been sitting well with astronomers for the past 40 years. Surely, these events don’t just happen based on how the mood strikes a black hole.

Apparently, the magnetic fields responsible for the very creation of these jets vary in stability. Given the right conditions, the twisting magnetic field radiating from a black hole can unleash a full-powered jet broad and strong enough to survive the bumps and barriers in its galaxy. Jets of this strength can cut through the galactic halo and spill out into space. Contrarily, an unstable magnetic field will propel a jet so narrow that it breaks apart at the slightest bump on the way, sending hot gas in different directions, warming up its galaxy.

Watch the simulation below.

“If I were to jump on top of a jet and fly with it, I would see the jet start to wiggle around because of a kink instability in the magnetic field,” says theoretical astrophysicist Alexander Tchekhovskoy, who is part of the research team. “If this wiggling grows faster than it takes the gas to reach the tip, then the jet will fall apart. If the instability grows slower than it takes for gas to go from the base to the tip of the jet, then the jet will stay stable.”

Regulating Supermassive Black Holes

So why is all this important, apart from the 40-year mystery finally unfolding?

Although the study has not gone far enough to explain what dictates the magnetic field’s stability variation (this might need an entirely different, possibly far more mind-boggling simulation altogether) it could explain why supermassive black holes do not get far more massive than they already are. Supermassive black holes cannot just keep growing and these regular events help regulate their size, which is great considering they are not picky eaters.

 

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