For the first time, astronomers have succeeded in taking a picture of the black hole in the center of our home galaxy, the Milky Way. The image presented on Thursday actually shows the surroundings of the supermassive black hole, because the objects themselves are inherently invisible.
The recording was made possible by observations with the “Event Horizon Telescope” (EHT), a merger of eight radio observatories on four continents to form a kind of super telescope.
The image of the mass monster at the heart of our galaxy is only the second image ever taken of a black hole. It shows a dark central region surrounded by a bright ring structure. Previously, only illustrations of the black hole at the center of the Milky Way have ever been seen in books and illustrative graphics.
The Max Planck Institute for Radio Astronomy (MPIfR) in Bonn is significantly involved in the EHT. The researchers present the results of their observations in a special edition of the “Astrophysical Journal Letters”.
The image of Sagittarius A* – the name of the black hole – is in good agreement with the predictions of Albert Einstein’s general theory of relativity for a black hole with four million times the mass of our sun, they report.
The hole is probably rotating. The Institute for Radio Astronomy in the Millimeter Range (IRAM), which is operated in German-French-Spanish cooperation and works with the 30-meter telescope in Spain and the NOEMA interferometer in France, was also involved in the measurements.
In 2019, the EHT researchers presented the first-ever image of the immediate vicinity of a black hole – also a glowing ring with a dark center. It was the much larger and more massive black hole at the center of galaxy M87, some 55 million light-years away.
Although the black hole at the center of the Milky Way is much closer to Earth at a distance of around 27,000 light-years, observations proved difficult. “The radiation from the black hole of M87 is constant for hours,” explained Anton Zensus from the MPIfR in Bonn, one of the main initiators of the EHT project.
“The object in the galactic center, on the other hand, changes over the course of just a few minutes. We therefore had to develop completely new methods for the evaluation.”
Astronomers believe that there is a black hole at the center of most galaxies. Because of their extreme mass, black holes don’t even let light escape, making them virtually invisible.
However, before being drawn into a black hole, matter heats up extremely and then glows brightly. This characteristic glow can be seen in the images in a reddish color.