New research shows that black holes found at the center of galaxies may be as large as 50 billion suns.
Professor Andrew King, from the University of Leicester Department of Physics and Astronomy, published a new study claiming that black holes that are directly in the center of galaxies could potentially grow to be 50 billion times the mass of our Sun, before they expend the “gas discs” they require to fuel their activity.
You can read Professor King’s paper on the study, titles ‘How Big Can A Black Hole Grow’, right here.
Hist study calculated the maximum size that a black hole could reach in theory. To derive the answer, King had to look at the regions surrounding the black holes themselves. Around a black hole gas settles into an “orbital disc” – here gas and matter loses energy and falls towards the black hole, feeding it. These discs can become unstable if they grow too large and do have a possibility to form into planetary masses, and even stars.
Due to the instability of the ring, the only way that a black hole could get larger, is if such planetary masses and stars formed in the discs, and the black hole’s gravity had caused them to fall inwards. But, since this would cause an instability that would no longer allow the black hole to grow (the disc it feeds on would begin to dissipate) – it’s believed that 50 billion suns is the upper mass for a black hole to grow – before stars form in it’s disc, and disrupt the balance.
In lamens terms, a black hole cannot outpace the formation of it’s disc. If it does, it will cease to grow. Therefore, 50 billion suns is seen as the limit for a black hole’s mass.
From here, the only way a black hole can get larger, is if it travels the universe, swallowing up other matter and slowly forming new orbital discs in new regions of space.
What this means for the study of black holes
“The significance of this discovery is that astronomers have found black holes of almost the maximum mass, by observing the huge amount of radiation given off by the gas disc as it falls in. The mass limit means that this procedure should not turn up any masses much bigger than those we know, because there would not be a luminous disc”
King goes on to say that if larger black holes formed, there would be no light whatsoever: “Bigger black hole masses are in principle possible—for example, a hole near the maximum mass could merge with another black hole, and the result would be bigger still. But no light would be produced in this merger, and the bigger merged black hole could not have a disc of gas that would make light.”
Thankfully, we shouldn’t need to worry about super massive black holes tearing through our cosmos undetected. We can seek out these black holes, for instance, observing as bent light rays pass close to the object; this is known as gravitational lensing.
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