The first image of a black hole in the center of the Messier 87 Galaxy published this week is amazing. The technology developed to create it is just as incredible. The Event Horizon Telescope (EHT) project brought together a network of 10 telescopes around the world and, as project director Sheered Doeleman says, "what we thought impossible to see".
Einstein first theorized the existence of black holes 100 years ago by developing his theory of general relativity. Since then, extensive evidence has shown the existence of back holes and simulations of their appearance, as they had not been observed directly.
So what took so long? Why did not we use something like the Hubble Space Telescope (HST) to take this picture?
While the black hole of M87 is as wide as our solar system, it is also 55 million light years away, which makes it very, very small in our sky. Each pixel of the HST WFC3 camera is about 1,250 times wider than the black hole. A telescope as big as the Earth was needed, so it was created, virtually.
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The radio telescopes of Hawaii, Arizona, Spain, Mexico, Chile and Antarctica were linked by a process called very long base interferometry to create a unique virtual telescope of the size of the Earth producing five petabytes of data. This is roughly the size of the Library of Congress digital collection or the equivalent of 190 years of continuous Netflix streaming in high definition.
It's not just a feat in astronomy, it's a feat in data science, especially reducing data and building images from sparse data.
Even with so much data and all that treatment, there were still many gaps. It's like assembling a puzzle where 90% of the pieces are missing and you do not even know what the final image is supposed to look like. So where does the assurance that the image published this week is accurate? The answer lies in the science of data.
Petabytes have been reduced to terabytes thanks to the correlation of observations between radio telescopes, which takes into account elements such as the rotation of the Earth during observations and the amount of water vapor in the atmosphere above of each telescope. The drought in the Atacama Desert in northern Chile, where one of the telescopes is located, made the job easier. This step also helps to extract useful data from noise, a common problem in data science.
EHT is divided into teams that have independently built algorithms to further reduce this data into an image, always trying to put together a puzzle with infinite possibilities, with missing pieces and no boxes with an image to which refer. Each built algorithms that reduced these infinite possibilities to only those that had a physical meaning. They came back together last July to share their work and they knew that they had solved the problem when the teams produced surprisingly similar results.
The resulting image processing techniques and libraries developed by the team could have far-reaching applications in areas requiring the construction of useful images from sparse data such as medical imaging and medical imaging. autonomous vehicles.
This black hole also now has a name, Pōwehi, which means "dark source embellished with endless creation". The name comes from Kumulipo, the primordial song describing the creation of the Hawaiian universe, reflecting the role of Mauna Kea's observatories in the creation of the image.
The Hawaiian astronomers of the project have consulted with Larry Kimura of the University of Hawaii at Hilo's College of Hawaiian Language. Hawaii Governor David Ige declared April 10 "Powehi Day".
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You can see Pōwehi, or at least his position in the southeast sky, after sunset. Look for the interrogation point back which constitutes the front of the Lion constellation, look below for the brilliant Spica star in the constellation of the Virgin. The M87 and Pōwehi galaxies are about 1/3 of the way from Virgo's left shoulder to Leo's tail.
Tony Rice is a volunteer with the NASA / JPL Solar System Ambassador Program and Software Engineer at Cisco Systems. You can follow him on Twitter @rtphokie.