The unexpected discovery suggests that black holes are more complex than anticipated.

According to a new study, black holes might be more complex than scientists have thought, which suggests for the first time that these mysterious objects might be exerting pressure on their environment.

Known for their potent gravitational force that draws everything from their neighborhood, black holes were initially considered entirely inert. Then, in 1974, renowned cosmologist Stephen Hawking discovered that these super-dense objects emit thermal radiation. A discovery by a team of scientists at the University of Sussex in the United Kingdom now points to an even more complex nature of these massive drains.

Astronomers Xavier Calmet and Folkert Kuipers concluded that black holes exert pressure as they studied the changes in gravitational forces caused by the behavior of quantum particles at the edge of black holes and the entropy, or the available energy, of that system.

As they ran their calculations repeatedly, an extra figure showed that they had no explanation. Eventually, they concluded this unaccounted variable must represent pressure.

"Our finding that Schwarzschild black holes [static black holes without electric charge and angular momentum] have a pressure, as well as a temperature, is even more exciting given that it was a total surprise," Xavier Calmet, Professor of Physics at the University of Sussex, and one of the authors of the new study said in a statement. "I am pleased that the research we are undertaking at the University of Sussex on quantum gravity has allowed science communities to understand the nature of black holes better."

The pressure exerted by the black hole, says Calm, is relatively weak. Still, its existence might help scientists improve their understanding of the behavior of black holes and how they marry the somewhat incongruous principles of quantum mechanics, thermodynamics, and gravity.

"If you consider black holes within only general relativity, one can show that they have a singularity in their countries where the laws of physics as we know they must break down," Calmet said. "It is hoped that when quantum field theory is incorporated into general relativity, we might be able to find a new description of black holes."

Folkert Kuipers, a doctoral researcher in the School of Mathematical and Physical Science at the University of Sussex and the second author of the paper, added: "It is exciting to work on a discovery that furthers our understanding; of black holes."Our result is a consequence of the cutting-edge research that we are undertaking into quantum physics at the University of Sussex, and it shines a new light on the quantum nature of black holes."