Photographing the edge of a black hole

One of the most interesting things about my job is that I get to learn about physics everyday. I never expected to embrace physics with such open arms, in fact, I used to dread it. It can be an intimidating area of science due to its abstract concepts and things don’t always make sense the first time around (especially when you go quantum). Thankfully, I have a great learning environment supported by an amazing team who encourages all my question asking. So today, I want to talk about one of our exhibits which is inspired by a current project that aims to uncover the mysteries of black holes.



A black hole forms following the death of a high mass star, which occurs when its core runs out of fuel (hydrogen), fuses into heavier elements and ultimately collapses on its own gravity. Since its gravitational collapse is so great, it begins pulling in everything nearby. Once things start to pass a boundary called the event horizon (a.k.a. the point of no return), nothing can escape it, not even light! Due to this phenomenon, we can’t see black holes and so scientists mainly rely on detecting radiation emitted by matter falling into them or observing how stars behave when they are close to black holes.  However, that’s all about to change. For the first time, scientists are trying to take a picture of the edge of the supermassive black hole (in Sagittarius A*)  thought to be at the centre of our galaxy. To do this, they are aligning twelve radio telescopes across the globe to create one large telescope, called the Event Horizon Telescope (EHT). Scientists are looking to: 1) test Einstein’s theory of general relativity, 2) further understand accretion (matter falling into a black hole) and 3) giant jets of matter around a black hole.

Our interactive exhibit demonstrates how the EHT generally works:


Visitors are encouraged to play with the radio telescope models and align them accordingly so that the picture of the edge of the black hole gets clearer. When the a radio telescope is aligned to the correct target (either Sagittarius A* or the black hole in M87), its corresponding picture on the screen will light up and the image of the black hole (in the middle) will change. If they stick around long enough, they will notice that certain telescopes change the image differently from the others.

The farthest telescopes set the boundary for the aperture. Of course, the actual telescopes are much more spread out than the ones in the exhibit.

Telescopes on the opposite ends (see arrows) help improve overall resolution through a process called aperture synthesis. Unlike our exhibit, the actual telescopes are much more spread out in order to create a telescope the size of Earth.

Lining up all the radio telescopes on one side will increase the sensitivity of the telescopes, making the image brighter. In some areas, there are more telescopes to increase their signals. However, aligning the telescopes farthest away from each other improves the resolution of the image, as it increases its array to give a footprint close to the size of earth; this helps define finer features. To put the EHT’s capability in another perspective, it would be like reading the date off a penny in Italy from Toronto. Data from this project will be collected sometime in April of this year so we’re hoping to see the final image put together before the tour ends. Maybe we could even incorporate it into the exhibit!

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