The First Black Hole Image: What is It and Why Should You Care?
From elementary school kids to senior citizens, the Event Horizon Telescope image is almost immediately recognized as a black hole. But why should you care?
This picture, released in 2019 by the Event Horizon Telescope Project, has already become one of the most recognized images in the world. But what is it, and why should you care about it? Those are the questions I’ll try to answer here briefly; I’ve also made a video version of this post that you can view here.
You’ve probably heard that it is a picture of a black hole, or more technically, the shadow of a black hole on light coming from hot gas that surrounds it. The image was acquired with radio telescopes, so the light is actually radio waves rather than the visible light that you might see with your eyes.
A picture of a black hole may sound amazing enough; after all, black holes, which are understood through Einstein’s general theory of relativity, are among the most exotic and mysterious objects in the universe. They are places where gravity has become so strong that not even light can escape from within them, but as the following illustration shows, their strong gravity can attract gas into orbit around them, and this gas becomes hot enough to emit light. In other words, the light comes from surrounding gas, not from the black hole itself.
Note that, contrary to a common myth, black holes don’t suck. As you might recall if you watched the movie Interstellar, it is possible in principle for stars, planets, or spaceships to orbit a black hole without ever getting sucked in. The surrounding gas falls in only because friction causes the orbits of gas particles to gradually decay.
This bring us to the question of why you should care about the first image of a black hole, and I’m going to argue that the answer goes far beyond the exciting science. To see what I mean, you have to understand a little bit about what it took to make the black hole image.
The image may look big on a screen, but we are looking at something that is really small, at least as viewed from Earth. This particular black hole is located at the center of a galaxy called M87, which is about 55 million light-years away. That means the light we see in the images below traveled through space for 55 million years before finally reaching our telescopes.
Given the size of this black hole, seeing it at the distance of M87 is the equivalent of trying to see a pinhead placed about 100,000 kilometers away! There is no single telescope in the world that is large enough to achieve this kind of resolution.
Fortunately, there is a remarkable technology called interferometry that can allow two or more smaller telescopes to work together to achieve the resolution of a much larger telescope. This technology has been particularly effective for radio telescopes, such as those of the Jansky Very Large Array in New Mexico (below left) and the ALMA array in Chile (below right). But these arrays are still too small to see a black hole.
Instead, the Event Horizon Telescope team realized that the only way they could get in image of a black hole would be to observe simultaneously with radio telescopes and arrays from all around the world, effectively making an Earth-size radio telescope; the map below shows the observatories that contributed to the first black hole image. (Even then, calculations showed that only two known black holes could in principle be imaged with current capabilities: the successfully acquired image of the central black hole of M87, and the black hole known to reside at the center or our own Milky Way Galaxy; the latter is still being worked on.)
Doing this required the effort of people and institutions from almost every country in the world, representing a multitude of races, religions, cultures, and genders. So why should you care? Here’s my answer…
We live in a world where the news may make it seem like everyone is always angry at each other. But imagine if someone — or our planet — suddenly shouted out “STOP! I need you to look at something…”
And imagine that the world listened and for at least a short while, people around the world decided to work together to do something that would not provide anyone any advantage over anyone else, or earn anyone any great wealth, but that would simply inspire all of us to realize what we can accomplish when we work together.
That is what the black hole image represents. Far more than a stunning scientific accomplishment, this image is a microcosm of the tremendous things that we can do when we put aside our differences and instead work together for the common good, and to advance human understanding of the world and universe in which we live.
The fact that the human race was able to make this image should therefore give you hope for our future; hope that we will learn to live together and take care of our small, fragile planet Earth. I’d even like to think that in some sense, it makes our mother Earth proud. And that’s why I think you should care about this first-ever image of a black hole.
To Learn More
- For details about the first black hole image, visit the Event Horizon Telescope Project web site.
- To learn more about black holes and relativity in general, please see my book What is Relativity? (Columbia University Press). Please also see my other books on the Big Kid Science web site.
- Watch the video version of this post on my Big Kid Science Youtube channel.
- You may also enjoy my video “What are Gravitational Waves and Why Should You Care?”:
