Seeing the unseeable

In April 2019 astronomers shared with the world a picture of one of the most mysterious objects in the universe. They had captured the very first image ever taken of a black hole. 

Black holes are places in space where a huge amount of matter is packed into a very small area. NASA suggests that it is the equivalent of a star ten times larger than the sun being squeezed into a sphere roughly the size of New York City.  Stuffing all that matter into such a small area creates a field of gravity that is so strong that nothing can escape its pull. And because light is one of those things consumed by it, observing a black hole directly has been near impossible. 

While scientists have studied black holes for a very long time no one had actually seen one. Instead scientists have had to infer the presence of black holes by studying their effect on matter around them; tracking star movement in the area or detecting large amounts of radiation.

Capturing the image was no small feat. More than 200 scientists worked for years to make it happen. It also took a network of eight telescopes placed at high altitudes around the world to work as one. This network, collectively known as the Event Horizon Telescope (EHT), linked locations including volcanoes in Hawai`i and Mexico, mountains in Arizona and the Spanish Sierra Nevada, the Chilean Atacama Desert, and Antarctica. This earth size telescope is so powerful you could use it to read a newspaper in New York, while sitting at a café in Paris!

The picture captured by the EHT shows a fuzzy bright orangey-red doughnut-shaped ring of dust and gas. This ring traces the outline of a black hole at the heart of the Messier 87 galaxy, 55m light years from Earth. The black hole is so big that it is 6.5 billion times more massive than our sun.

The brilliant oranges and reds captured by the EHT are the radiation emitted by particles of matter heated to billions of degrees as they swirl around the black hole before vanishing into it. The dark shadow within that ring marks the edge of the event horizon. At that point no light or matter can travel fast enough to escape the black hole’s irresistible gravitational pull. 

While the image has answered a number of questions, like all good discoveries, it has challenged scientists to answer many more, the biggest of which is what lies at the centre of those mysterious black holes in the universe?

Wrap your head around this: At the event horizon, light is bent in a perfect loop around the black hole, meaning if you stood there you would be able to see the back of your own head.

Face behind the science

Computer scientist Katie Bouman started working on the black hole image project as a 23 year old graduate student. She came up with a way to turn the overwhelming amount of data collected by the eight telescopes into a single visual image.

Article originally published in Brainspace Magazine Fall 2019

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