May 17, 2022
Melinda Head

Our Supermassive Black Hole: Einstein Got It Right

It’s the stuff of science fiction and it’s totally jaw-dropping

Call it what you will – a black hole, a donut, Sagittarius A* or Sgr A* for short (pronounced A-star). It’s the first black hole to be seen in our own backyard – the Milky Way Galaxy.

Our sun (which is actually a star) and all the planets around it (including earth) are part of a galaxy known as the Milky Way. A galaxy is a large group of stars, gas and dust bound together by gravity. Sagittarius A* could be described as the gatekeeper of our galaxy, as absolutely nothing can pass through it.

Albert Einstein predicted the existence of black holes – points in space where gravity is so strong that neither particles nor light can escape from them – more than a century ago. Back then, pen and paper and chalk on a blackboard were his tools. His general theory of relativity has passed all tests physicists have devised so far, and continues to underlie our understanding of space, time and gravity. The idiosyncratic man with notoriously bad hair whose ashes are scattered on the grounds of Princeton University’s Institute for Advanced Study, was quite a man indeed. Einstein would be 143 years old today.

Recipient of the 1921 Nobel Prize in Physics, Albert Einstein, was a German-American theoretical physicist, best known for developing the theory of relativity and contributing to the development of the theory of quantum mechanics

How was an image of our galaxy’s elusive black hole captured? No single observatory has yet been designed to do so on its own. Instead, a planet-spanning network of radio dishes, called the Event Horizon Telescope (EHT), was used to create an aggregation of images to form a single “earth-sized” virtual telescope. The telescope is named after the “event horizon”, the theoretical boundary around a black hole, which some have called the point of no return.

To piece together an image of A-Star, multiple static observations were joined together from huge radio dishes in different places across the world

The anatomy of a black hole

Way back in April 2017, the EHT network captured 3.5 petabytes of data (the equivalent of 3.5 million gigabytes), after which researchers began piecing together an image of Sgr A* from a massive amount of data. This collective effort from more than 300 researchers working at 80 prestigious institutes has taken 5 years. COVID-19 accelerated the process, as other celestial work had to be slowed down or put on hold, leaving extra time for investigators to pour over Sgr A* data.

The next-generation Event Horizon Telescope (ngEHT) was launched in 2019 and will more than double the number of radio dishes, both filling in gaps, modernizing existing instrumentation and adding new capabilities in the quest to discover even more truths about the universe. My guess is: we ain’t seen nothin’ yet. Stay tuned!

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About the Author

A serial entrepreneur, Melinda is a sociologist and statistician who believes there is no currency with greater value than knowledge

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