The picture was made possible through 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.
While the team acknowledged the visual similarities between the new picture and 2019’s M87 * image, 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 down to the gas surrounding Sagittarius A * completing an orbit in just minutes, compared to the days to weeks it takes to orbit the much larger M87 *, causing the brightness and pattern of the gas to change rapidly. The team compared capturing it to being “a bit like trying to take a clear picture of a puppy quickly chasing its tail,” leading them to develop sophisticated new tools to account for gas movement to make the black hole visible.
“If Sagittarius A * were the size of a donut, 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. “