Do you remember the first image of a black hole in our galaxy? we take it

Black holes are among the most profound predictions of Einstein’s theory of general relativity. Originally studied as a mere mathematical consequence of theory rather than physically relevant objects, they were soon seen as generic and sometimes inevitable results of the gravitational collapse that initially forms a galaxy.

In fact, most physicists have suspected that our own galaxy revolves around a supermassive black hole at its center. There are other ideas as well, such as “dark matter” (an invisible substance thought to make up most of the matter in the universe). But now an international team of astronomers, including a team I led from the University of Central Lancashire, has revealed the first image of the object lurking at the center of the Milky Way, and it is a supermassive black hole.

This means that there is now overwhelming evidence for the black hole, dubbed Sagittarius A*. While it might seem a bit scary to be this close to such a beast, it’s actually about 26,000 light-years away, which is reassuringly far. In fact, because the black hole is so far from Earth, it appears to us to be about the same size in the sky as a donut on the Moon. Sagittarius A* also seems quite inactive: it is not devouring much matter from its environment.

Our team was part of the global Event Horizon Telescope (EHT) Collaboration, which has used observations from a global network of eight radio telescopes on our planet, collectively forming a single virtual Earth-sized telescope, to take the stunning image. The breakthrough follows the collaboration’s 2019 release of the first image of a black hole, called M87*, at the center of the more distant Messier 87 galaxy.

looking in the dark

The team observed Sagittarius A* over several nights, collecting data for many hours at a time, similar to using a long exposure time on a camera. Although we can’t see the black hole itself, because it’s completely dark, the glowing gas surrounding it reveals a telltale signature: a dark central region (called a “shadow”) surrounded by a bright ring-like structure. The new view captures light deflected by the powerful gravity of the black hole, which is four million times more massive than our Sun. The discovery also sheds valuable clues about the workings of black holes, which are thought to reside at the center of Earth. most galaxies.

Image from ALMA – one of the Event Horizon telescopes.