It was once thought to be impossible to capture a photo of a black hole until it happened. But how exactly did scientists do it?
In 2019, one of the greatest modern-day scientific achievements was revealed: a photo taken of a black hole. Before then, any photo you might’ve been depicting a black hole was only a prediction of how one might appear. (Yes, that includes the photo above, too!)
Evidence of black holes has existed for a while, but the problem was being able to observe one. As the name suggests, a black hole is an area of space where no light is reflected, and gravity is so strong that nothing can escape from it. Anything that comes near a black hole is subjected to be consumed and never re-emerge. Since even light cannot escape, it would be impossible for anyone to observe a black hole in traditional ways.
Instead of taking a photo of the black hole directly, scientists opted on capturing the black hole’s silhouette instead. Near the black hole’s event horizon, the boundary separating the black hole from the rest of space is an area of super-hot gases that swirl around the event horizon. These gases shine at a large range of wavelengths of light, allowing them to be easily visible among the dark plane of space. Against this bright background, the shadow of the black hole can be distinctly seen.
However, this was far from easy. The target black hole at the center of the galaxy Messier 87 (or M87) is 55 million light-years away, with a diameter of 40 billion kilometers; for context, it would appear on Earth to be about the size of an orange on the surface of the moon. Despite its small size compared to other celestial bodies, the M87 black hole has consumed the mass equivalent to 6.5 billion times the mass of the Sun.
No existing telescope has the ability to capture an image from 55 million light-years away. A telescope would have to be the size of the Earth in order to see anything from that far away. This was clearly impossible, so scientists came up with the next best solution: forming a global organization to coordinate multiple telescopes from around the world.
The Event Horizon Telescope project, consisting of over 300 scientists and working in over 20 different countries, created a network that allowed images to be created from multiple telescopes. By focusing on a single object at the same time, all of the telescopes together were able to produce an image similar to one an Earth-sized telescope could. This mechanism required a lucky gamble; the telescopes must all be precisely coordinated and be in areas of clear weather as to not interact with telescope waves. The initial image data was collected in April of 2017.
After collecting all the data, the hardest part began. Analyzing the data took about two years before the image could be finalized. The amount of data collected was too large to transfer digitally, so it had to be transported as hard drives that contained around 5 petabytes. For reference, 5 petabytes worth of data as MP3s would take 5000 years to play.
With this data, scientists were able to slowly piece together the final image of the black hole. This process consisted of four individual teams, each testing their own algorithms and models for the image. In the end, the images developed by each team were very similar, meaning that the final image was the most accurate possible.
What once seemed impossible became one of science’s greatest accomplishments. On April 10, 2019, the photo of M87 was revealed to the public, marking the end of a long and difficult journey for the Event Horizon Telescope group. While a singular photo might seem insignificant, the efforts of the group opened the door to more research and discoveries regarding black holes, and to possibly unlock more secrets of the universe.
Thanks for reading!
Written by Kaylee Barrera
Sources
About. https://eventhorizontelescope.org/about. Accessed 20 July 2021.
Choi, Charles Q. “Historic 1st Photo of a Black Hole Named Science Breakthrough of 2019.” Space.Com, https://www.space.com/first-black-hole-photo-science-breakthrough-2019.html. Accessed 20 July 2021.
Clery, Daniel. “For the First Time, You Can See What a Black Hole Looks Like.” Science | AAAS, 10 Apr. 2019, https://www.sciencemag.org/news/2019/04/black-hole.
“First-Ever Picture of a Black Hole Unveiled.” Science, 10 Apr. 2019, https://www.nationalgeographic.com/science/article/first-picture-black-hole-revealed-m87-event-horizon-telescope-astrophysics.
“How Scientists Captured the First Image of a Black Hole - Teachable Moments.” NASA/JPL Edu, https://www.jpl.nasa.gov/edu/news/2019/4/19/how-scientists-captured-the-first-image-of-a-black-hole/. Accessed 20 July 2021.
Loff, Sarah. “Black Hole Image Makes History; NASA Telescopes Coordinate Observation.” NASA, 10 Apr. 2019, http://www.nasa.gov/mission_pages/chandra/news/black-hole-image-makes-history.
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