The supermassive black hole at the heart of our Milky Way galaxy has been photographed for the first time, giving astronomers invaluable insight into how black holes interact with their surroundings.
The object, known as Sagittarius A*, was captured by the Event Horizon Telescope Collaboration, the same global team that took the famous first-ever picture of a black hole inside the Messier 87 (M87) galaxy in 2019. Although the hole itself is entirely dark, it’s encircled by a bright ring of glowing gas that’s been warped by hole’s own gravity.
The picture was made possible by linking eight existing radio observatories across the globe to form a single “Earth-size” virtual telescope that collected data for many hours across multiple nights.
This new image might look very similar to the 2019 one of M87*, but the masses of the two black holes and the types of galaxies surrounding them are very different. The researchers were able to work out that Sagittarius A*, which sits at the center of our small spiral galaxy, consumes gas at a much slower rate than M87*, which resides at the center of a giant elliptical galaxy and ejects a powerful jet of plasma.
Despite being much closer to us, Sagittarius A* was significantly more difficult to capture than M87*. This is because the gas surrounding Sagittarius A* completes an orbit in just minutes compared with days to weeks for the gas orbiting the much larger M87*, causing the brightness and pattern of the gas to change rapidly. The team compared capturing it to “trying to take a clear picture of a puppy quickly chasing its tail.” To make the black hole visible, they developed sophisticated new tools to account for the gas movement.
“If Sagittarius A* were the size of a doughnut, M87* would be the size of the Allianz Arena, the Munich football stadium just a few kilometers from where we are today,” Sara Issaoun, NASA Einstein fellow at the Harvard & Smithsonian Center for Astrophysics, told a press conference at the European Southern Observatory in Germany. “This similarity reveals to us a key aspect of black holes no matter their size or the environment they live in. Once you arrive at the edge of a black hole, gravity takes over.”