The Event Horizon Telescope (EHT) collaboration has released the highest resolution image of a black hole thousands of light-years away.
A black hole is a place in space where gravity is so strong that even light cannot escape its pull. According to NASA, gravity in black holes is so strong because matter has been squeezed into a tiny space and even light cannot escape. In the darkness of space, black holes are invisible.
To discover such a mysterious object, conventional telescopes on Earth are not sufficient.
Astronomers are therefore turning our entire planet into a giant virtual telescope called the Event Horizon Telescope (EHT). This groundbreaking project has been able to capture unprecedented images of supermassive black holes at the centers of galaxies, including our own Milky Way.
The earth becomes a giant telescope
The EHT achieves this by using a technique called very long baseline interferometry (VLBI), which connects radio telescopes around the world to create an Earth-sized observatory.
By combining data from multiple telescopes, the EHT can achieve a resolution equivalent to reading a New York newspaper in a Paris street café.
This project focuses on several important observatories, including the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, the Submillimeter Array (SMA) in Hawaii, and telescopes in Spain, Mexico, and even the South Pole.
These facilities simultaneously observe a specific black hole and record huge amounts of data on hard drives, which are later transported to central processing centers.
The EHT operates at a frequency of 230 GHz (a wavelength of 1.3 mm), which allows it to see through the dust and gas that often obscure the centers of galaxies. This frequency is crucial for observing the immediate environment of black holes, where the effects of extreme gravity can be directly studied.
To create the highest resolution image, the observable frequency was changed to 345 GHz.
IT IS NOT EASY
One of the biggest challenges in this project is synchronizing observations on different continents. To achieve the required precision, each telescope is equipped with an atomic clock accurate to a fraction of a trillionth of a second.
This synchronization ensures that data from all sites can be combined coherently, creating a virtual telescope with unprecedented resolution.
The enormous amount of data collected during an observation run – measured in petabytes – is too large to transmit over the Internet.
Instead, the hard drives are physically transported to supercomputer centers at the Max Planck Institute for Radio Astronomy in Germany and the MIT Haystack Observatory in the US. Here, the data is processed using special algorithms to create the final images.
Finding the black hole
The EHT’s first major success came in 2019 with the publication of the very first image of a black hole at the center of the galaxy M87.
This groundbreaking achievement was followed in 2022 by an image of Sagittarius A*, the supermassive black hole at the heart of our own Milky Way.
Looking to the future, the EHT team is working to improve the array’s capabilities by adding new telescopes and achieving higher frequencies.
These advances promise even sharper images and the potential to create “movies” of black holes, providing unprecedented insight into the behavior of these cosmic giants and allowing Einstein’s general theory of relativity to be tested in the most extreme environments in the universe.
