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The black hole at the centre of galaxy M87EHT Collaboration
By Leah CraneThe Event Horizon Telescope (EHT), which uses a network of telescopes around the globe to turn the Earth into an enormous radio telescope, has taken the first direct image of a black hole.
This image shows the large black hole in the centre of another galaxy called M87, which is 55 million light years away. This is the first ever real image of a black hole – previous images have been simulations.
Here’s everything you need to know about the images from the Event Horizon Telescope.
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How is it possible that a picture of a black hole was taken? Don’t black holes suck everything in, including light?
The picture is of the black hole’s silhouette against the bright material circling it. Nothing we can see is coming out of the black hole.
How big is the EHT black hole?
M87 is about seven billion times the mass of the sun, and about 100 billion kilometres wide – which could easily swallow our solar system. This is about 22 times the average distance between Neptune and the Sun.
The EHT researchers have been observing two black holes. Why didn’t they release a picture of both of them?
In 2017, the eight telescopes of the EHT collaboration observed two supermassive black holes: the giant one at the centre of our galaxy, Sagittarius A*, and a much larger black hole at the centre of another galaxy, called M87.
They’ve focused all their energy so far on making this image of M87, which is easier as it is bigger and less obscured. It’s really hard to put all the data together to make an image, but there will be a Sagittarius A* image eventually.
Where is the event horizon?
The event horizon is in the black area – the shadow of the black hole against the material circling it, and eventually falling in.
An image of the black hole in galaxy M87 provided by NASA’s Chandra X-ray ObservatoryNASA/CXC/Villanova University/J. Neilsen
Why is the image brighter on one side?
It’s brighter on one side because it’s rotating – the light that’s coming toward us appears brighter, and the light that’s moving away doesn’t appear as bright.
How exactly does the EHT black hole image impact quantum mechanics and general relativity? Will it affect the laws of physics?
So far, the new image is consistent with general relativity. The hope is that eventually, when we can observe the event horizon with higher resolution, it will help us figure out how quantum and relativity mesh together because it’s such an extreme area.
Is it the accretion disk or the black hole that is rotating? Is the EHT black hole a Kerr black hole or not?
From this image, we can’t be totally sure whether it’s just the accretion disk rotating, or just the black hole, or both.
Weren’t tiny black holes made here on Earth with the Large Hadron Collider?
No. Some people were concerned the Large Hadron Collider would make mini black holes, but it did not. It would require much more energy than the collider can produce to do that.
Have we proven Hawking radiation or is it just a theory?
Hawking radiation is very difficult to prove experimentally or observationally, and has never been observed. It is still theoretical – for now, it is a purely theoretical quantum effect.
These answers were provided by our science reporter Leah Crane answering questions from New Scientist readers on Twitter. Read her full Twitter Q&A here.
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