Our universe continues to baffle scientists even today and one of the greatest mysteries of all is what black holes are.
Some of the greatest scientific minds throughout history like Albert Einstein and J. Robert Oppenheimer have come up with their own theories about black holes.
Today marks the 85th anniversary of the Oppenheimer-Snyder model, which proved for the first time in contemporary physics how black holes could develop following Einstein’s field equations.
Professor Nils Andersson is a Professor of Applied Mathematics at the University of Southampton and is an expert on astrophysics and black holes.
He told Metro about the importance of Oppenheimer’s findings and said: ‘The paper was in many ways remarkable. The abstract could almost be written today as very little has changed.
‘The main impact of the paper came in the 1960s and later when general relativity had a renaissance associated with the birth of x-ray astronomy.’
Because of this later discovery, Professor Andersson believes Oppenheimer and Synder’s initial findings did not help people’s understanding about black holes to begin with.
‘It is more a what could have been than anything else,’ he said.
‘Shortly after the paper appeared, Oppenheimer turned his attention to other aspects of relativity.
‘Black holes were not understood at all at the time. The phrase was not even coined until the 1960s.’
It was Einstein who first predicted the existence of black holes in 1916, with his general theory of relativity.
But the term ‘black hole’ was not coined until many years after Einstein and Oppenheimer’s groundbreaking discoveries – 1967 in fact.
American astronomer John Wheeler was the first person to call it a black hole after decades of them only being known as theoretical objects.
Nasa confirmed in 1964 that the first signs of a black hole were discovered in the Milky Way when a sounding rocket detected celestial sources of x-ray.
Scientists later found these x-rays were coming from a bright blue star orbiting a strange dark object.
These early findings and scientific discoveries helped shaped experts understanding around the mystery of black holes today.
The first-ever image of a black hole was recorded by the Event Horizon Telescope (EHT) in 2019.
It was spotted in the centre of galaxy M87 and shows the sudden loss of particles of light and has helped open up a whole new area of research into black holes, now that scientists know what they look like.
The same black hole was then pictured in polorised light in 2021 which made it clear that the hole’s rings are magnetized.
Professor Andersson said findings like this has helped strengthened our understanding around black holes.
One theory suggests that if you fell through a black hole you would stretch out like spaghetti, but sadly die before this happened.
Another theory suggests that quantum effects would cause somebody to burn to death instantly.
Black holes don’t suck. Instead, objects fall into them because they fall toward anything that exerts gravity, like the Earth.
If a star passes too close to a black hole it is torn apart.
There are an estimated 10 million to one billion black holes in the Milky Way alone.
He said: ‘We know black holes are well described by Einstein’s curved spacetime theory and that they are very common.
‘They come in a variety of sizes, with absolute giants at the centre of most galaxies.
‘From gravitational wave observations we know that smaller ones – a few to ten times as heavy as the sun – are very common.’
But there are still some mysteries for the experts to uncover.
He continued: ‘In my opinion, if they are truly the objects described by Einstein’s theory, precision observations, most likely via gravitational wave astronomy, will provide better answers.
‘The event Horizon Telescope results are also useful but it is debatable if they can be used to get the answers we are looking for.
‘Next generation gravitational wave interferometers should see black hole collisions throughout the universe, which is quite exciting because we may learn how they form and evolve.’
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