The picture was made possible by linking eight existing radio observatories across the globe to form a single “Earth-sized” 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 that 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.”