The first-ever image of a black hole

Ring of fire: The halo of gas and light represents the black hole’s “event horizon”. © EHT

This week, scientists released the first-ever picture of a black hole, compiled over the last two years using data from eight telescopes around the world. It is a major landmark in the history of physics.

“It is quite stunning,” Michael Kramer from the Max Planck Institute told the Financial Times yesterday. “History books will be divided into the time before the image and after the image.”

He was speaking of the world’s first-ever picture of a black hole, revealed by scientists on Wednesday.

It lies at the centre of the M87 galaxy, 55 million light years away. It is a “supermassive” black hole: at 40 billion kilometres across, it is larger than our entire solar system. Its mass is 6.5 billion times that of our Sun.

“It is an absolute monster, the heavyweight champion of black holes in the universe,” said Professor Heino Falcke (who first proposed the experiment) to BBC News.

The image was first captured over a period of ten days in 2017 by the Event Horizon Telescope, a network of eight telescopes positioned around the world. It has taken scientists two years to compile the vast amounts data into a single image.

Scientists once thought this kind of supermassive black hole was rare — but many more have been discovered in recent years. They now think that there is one at the centre of most galaxies, including our own. So what exactly are they?

Normal-sized stellar black holes were predicted by Einstein 100 years ago. He realised that the fabric of the universe is made of space-time, and that large objects like planets distort it — imagine bowling balls resting on a trampoline and curving its surface towards them. We experience this as gravity.

When a large enough star collapses, its gravity becomes so strong that it pulls the fabric of space-time into a “hole” that not even light can escape. At its very centre, time itself will stop. This is a black hole.

They are still some of the strangest and most mysterious objects in the universe. But this image could bring us closer to understanding. Astronomers will be able to compare the real-life image to the theories predicted by physics, looking for inconsistencies that could provide answers to their questions — or raise new questions altogether.

Universal

For some, these are scary thoughts. Giant holes in the sky, eating up stars and stopping time? Earth is not in danger from black holes but it is unsettling to think that anything so strange and powerful even exists. The more we discover about the universe, the more powerless humans seem in contrast.

Others find it inspiring. When supermassive black holes are active they release radiation, helping to form the galaxies surrounding them. The black hole at the centre of our own galaxy is now quiet — but it once played a crucial part in creating our solar system. Even the most terrifying things in space have had an important role in our lives. Isn’t that wonderful?

You Decide

  1. Is the thought of supermassive black holes cool or scary?
  2. Stephen Hawking believes black holes could be “portals” to other universes. If this is true, would you want to travel through one?

Activities

  1. Draw a diagram of a galaxy with a supermassive black hole at its centre.
  2. Write a list of three questions about the universe that you would like answered. Then swap lists with a partner, and research the answers to each other’s questions.

Some People Say...

“The most beautiful thing we can experience is the mysterious. It is the source of all true art and science.”

Albert Einstein

What do you think?

Q & A

What do we know?
That black holes are incredibly hard to study. Since nothing can escape a black hole — including light — there is nothing for telescopes to observe. But we can see the bright ring of gas and light at the very edge of the black hole, known as its “event horizon” (or the point of no return). The hole at the centre is the “shadow” of the black hole itself.
What do we not know?
A lot. What would happen if you fell into a black hole? What are supermassive black holes made of? Where do they lead? How are they even formed? We do have some theories about their formation, including: (1) the collapse of massive clouds of gas; (2) stellar black holes which consume so much they become giant; (3) lots of stellar black holes combine.

Word Watch

Light years
About 5.88 trillion miles, or 9.5 trillion kilometres. This is the distance that light travels in a single Earth year.
Event Horizon Telescope
Eight linked radio telescopes located around the globe. Working in synchronization, they are much more effective than any single telescope.
Data
There was so much data that it couldn’t be sent by computer. Instead, it was stored on hundreds of hard drives that were then flown to processing centres. A 29-year-old computer scientist, Katie Bouman, developed the algorithm which produced the image.
Stellar black holes
These are about 10 to 24 times larger than the Sun. When a massive star collapses at the end of its life, its gravity makes it smaller and smaller until it has zero volume — this is the moment the black hole forms.
Space-time
Space is so closely related with time that, in the early 20th century, scientists began to think of them as the same thing. This is space-time. When it warps, it produces gravity. Imagine a marble rolling around the bowling ball on the trampoline — that is how the Moon orbits the Earth.

Subjects

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