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Astronomers observe light from behind a black hole for first time


An artists’ illustration of a black hole (Picture: Getty)

Light from behind a black hole has been observed by astronomers for the first time.

When a solar eclipse occurs, the sun is blocked out by the moon. We can’t see the sun because the moon is blocking the light’s path from the sun.

A similar blocking of light should also occur for black holes, super dense bodies of matter that lie at the heart of most galaxies.

But something different happens – because black holes are so heavy, they bend the path of light around them.

Albert Einstein predicted this effect in his ground-breaking theory of general relativity, published more than 100 years ago.

But researchers at the University of Stanford have now observed the effect in nature for the first time.

Astronomers were studying bright X-ray flares from a supermassive black hole, a relatively normal observation, in the centre of galaxy I Zwicky 1 more than 800 million light years away.

But alongside the bright X-ray flares, a different signal was picked up – unexpected ‘luminous echoes’ that were smaller and of a different energy than the flares.

One of the astronomers that observed the echoes realised that they lined up with his predictions of what light from behind a black hole might look like.

‘I’ve been building theoretical predictions of how these echoes appear to us for a few years,’ said astrophysicist Dan Wilkins.

‘I’d already seen them in the theory I’ve been developing, so once I saw them in the telescope observations, I could figure out the connection.’

The discovery, published in Nature on Wednesday, is a further confirmation of Einstein’s theory of relativity, which is already used in GPS technologies the world over.

This is the first picture of a black hole, released by astronomers in 2019 (Picture: Getty)

Einstein predicted the light-bending properties of very massive objects in 1915.

‘Any light that goes into that black hole doesn’t come out, so we shouldn’t be able to see anything that’s behind the black hole,’ said Stanford astrophysicist Wilkins.

‘The reason we can see that is because that black hole is warping space, bending light and twisting magnetic fields around itself.’

The direct observation of black holes is a relatively recent phenomena, with the first picture of a black hole taken in 2019.

Roger Blandford, a co-author of the research, published in Nature, said: ‘Fifty years ago, when astrophysicists starting speculating about how the magnetic field might behave close to a black hole, they had no idea that one day we might have the techniques to observe this directly and see Einstein’s general theory of relativity in action.’

Wilkins and his team originally set out to learn more about a black holes’ corona, the ring of ultra-hot gas particles that form around a black hole.

Researchers best guess about the coronas’ formation is that the extreme magnetic fields of the black holes separate electrons from atoms as the gas moves into the black hole, creating ‘magnetised plasma’ floating around the edge of the body.

‘Caught up in the powerful spin of the black hole, the magnetic field arcs so high above the black hole, and twirls about itself so much, that it eventually breaks altogether – a situation so reminiscent of what happens around our own Sun that it borrowed the name “corona”,’ explains Wilkins.

‘This magnetic field getting tied up and then snapping close to the black hole heats everything around it and produces these high energy electrons that then go on to produce the X-rays.’


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