Maltese scientist discovers black holes growing faster

Black holes can expand by ‘eating’ gases near them.

Black holes can expand by ‘eating’ gases near them.

Research led by a Maltese astronomer has shown that black holes are growing much faster than originally believed by ‘absorbing’ nearby gases.

Scientists previously believed that the mysterious entities could only grow when galaxies collided with one another, creating huge concentrations of hot gas around black holes.

But Victor Debattista and his fellow researchers have now proven that even more isolated black holes in less volatile galaxies can grow extremely quickly.

They reckon that a black hole in our own galaxy, the Milky Way, absorbs the amount of mass our sun is made of every 3,000 years. One black hole, found in the Sombrero galaxy, has been swallowing the equivalent of one sun every 20 years.

Dr Debattista, who lectures at the University of Central Lancashire and the University of Malta, made the discovery following a series of computer simulations, many of which were carried out on the University of Malta’s supercomputer.

“The simulations showed how black holes can expand by ‘eating’ gases near them. And that discovery has been further confirmed by observations made through the Hubble Space Telescope,” he said.

His research team, which included Yale University astro­nomer Frank C. van den Bosch and Ohio State University astro­nomer Stelios Kazantzidis, has been studying the behaviour of black holes for the past seven years.

A paper describing the team’s findings has been published in The Astrophysical Journal, and Dr Debattista told The Times the findings had been very well received by the astrophysical academic community.

He now hopes to take his research a step further. New knowledge about the way in which black holes grow can help scientists discover at which point in the past black holes grew fastest; it will also lead to a better understanding of the differences between black holes in gas-poor galaxies and those in more gaseous ones.

Black holes – essentially what is left when a massive star dies – continue to intrigue and perplex scientists, decades after physicist Albert Einstein’s theory of relativity helped scientists discover them.

But if Dr Debattista’s findings mean black holes can grow by merely sucking in nearby gases, what is to stop them from expanding endlessly until they subsume entire galaxies?

The wide-eyed question prompts a chuckle from the UK-based Maltese scientist. “Things must lose their angular momentum – their spin – to fall into a black hole. Stars cannot do that.”


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