A photo of a black hole at the center of the Milky Way has been unveiled by astronomers working on the Event Horizon Telescope collaboration. Although this isn’t the first time astronomers have photographed a black hole, it is the first time they’ve managed to capture one in our own galaxy.
Black holes are a region of spacetime where gravity is so strong that no particles or light can escape them. They are thought to be found at the center of most galaxies and are created when massive stars explode in an astronomical event known as a supernova. The first black hole was photographed in 2019 and is known as M87* in a galaxy that's 53.49 million light years from earth.
These photos of the black hole known as Sagittarius A* (SgrA*, pronounced sadge-ay-star) confirm scientists' theories based on observations of stars orbiting something invisible and massive. Since black holes absorb all light, we cannot observe the black hole itself but we can see the glowing gas that surrounds a dark central region in a ring-like structure.
Even though this black hole is much closer to Earth than the black hole known as M87* found in the distant Messier 87 galaxy, photographing it proved to be a much bigger challenge. The reason for this is because SgrA* is smaller than M87* so the gas that orbits it takes just a couple of minutes to complete an orbit rather than a matter of weeks so the image is constantly changing.
SgrA* is about 27,000 light-years away from Earth and in order to photograph it astronomers created the Event Horizon Telescope which linked together eight existing radio observatories across the planet to form a single ‘Earth-sized” telescope. Over a series of nights, the EHT observed SgrA*, compiling hours' worth of data just like you would if you were photographing a night sky using bulb mode.
One of the scientists working on the EHT collaboration is Geoffrey Bower from the Institute of Astronomy and Astrophysics, Academia Sinica in Taipei. "We were stunned by how well the size of the ring agreed with the predictions from Einstein's Theory of General Relativity," he said of the observations made by SgrA*.
"These unprecedented observations have greatly improved our understanding of what happens at the very center of our galaxy and offer new insights on how these giant black holes interact with their surroundings."
The results from the EHT findings will be published in a special edition of The Astrophysical Journal Letters (opens in new tab) and the EHT will continue to expand its network of telescopes. Scientists hope that the ongoing expansion and technological advances will one day enable them tp capture even better photos of black holes and possibly even videos.