Black Hole Photography
Or, how to make a telescope as large as the world
This is it. The first image that has ever been taken of any black hole.
And maybe it doesn’t look spectacular at first, but consider this: not only is this black hole is about 55 million light years away from us, but black holes are invisible by their very nature! (This is because their gravitational pull is so strong that not even light can escape them.)
Which is why, for many years, astronomers thought that an image of a black hole would be impossible to get.
They were wrong.
In theory, we can’t take a picture of a black hole because it just isn’t possible to take an image of something that doesn’t emit or reflect light.
Take a closer look, though. What you see in the picture is not the black hole itself, but a disk around it. You’ll see black space, a ring of fire, and then more black within.
That’s the black hole.
In this picture, the black hole isn’t visible — and shouldn’t be, if our laws of physics are correct.
The ring itself exists because of a phenomenon in which a star comes too close to the black hole and gets sucked into it.
Due to the enormous amount of gravitational force exerted by the black hole, the star gets pulled in until all that remains is the ring. The ring is called the accretion disk, and it’s the most obvious part of the image taken.
But it won’t be around forever: the black hole continues to exert it’s pull, and after a period of time, this ring will get eaten up as well.
The story begins with a small team of innovators and ends with a telescope that is unlike anything the world has ever seen.
Although there have been major advances in telescope technology lately, there is no single telescope on earth that can take a picture of a black hole. They’re just too small to do so!
In theory, to have that kind of resolution, you would need a telescope the size of planet Earth, and obviously, that isn’t possible. To solve this problem, they hit upon an idea that was truly innovative: if one telescope couldn’t do the job then perhaps many would.
As it turns out, they were right.
The team used a global network of dishes to simulate a telescope of this size. Twelve radio-telescopes stationed at different points across the world were kept in sync with powerful atomic clocks. Each telescope collected and recorded radio waves coming from near the black hole. This data was then combined using supercomputers to create the image of the black hole.
This program included the support of many countries and was named the Event Horizon Telescope or EHT.
This black hole is actually what’s called a supermassive black hole that lives in the centre of the Messier 87 galaxy. It’s about 7 billion times as massive as our Sun. That’s colossal compared even to other supermassive black holes.
The most important part of this photo is where there is no light, that dark circle in the centre which measures to about 25 billion miles across. That’s the actual black hole.
And at its edge is the place known as the event horizon, the point of no return. Once you cross the event horizon, the black hole’s gravity is so strong that you cannot escape. Not you, not the fastest spacecraft, not even the fastest thing in the universe: light.
Many, many things needed to be just right in order to capture this image, enough that it might be considered a miracle. The light travelled for about 55 million light years, without getting absorbed by gas or particle. Only a small fraction of the radio waves that hit the outer atmosphere actually end up reaching the surface, as most of them get absorbed or reflected. And for these waves to get received by the EHT, the weather needed to be good and clear at every one of the 12 telescopes, including the one in Antarctica.
This is the first picture of a black hole ever taken, but it certainly isn’t the last.
As after this first success, the team of EHT Scientists has started examining other black holes, in hopes to further our understandings on the black holes.
The team has now turned the giant camera towards another black hole named the Sagittarius A*. This black hole is the one present at the center of our own galaxy, the Milky Way. We believe that its images will be released soon.
With these images of black holes, we can understand more about their properties and answer currently unanswered questions like:
Why are they present at the centre of galaxies?
Why do they vomit massive streams of subatomic particles into space?
How exactly do they affect the space-time fabric around them?
And, what effect might they one day have on us?
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