It was also noticeable to the scientists how emotional and with how much excitement this announcement was, which the European Southern Observatory ESO had announced as a "groundbreaking result of the Event Horizon Telescope project" for Thursday, 3 p.m.

They came from all over Europe in the Eridanus Hall of the ESO headquarters in Garching to present what more than three hundred scientists from over 20 countries had achieved together after years of work and decades of preparation.

The day before there had been a dress rehearsal that was strictly closed to the public, because the timing, which scientists tend to lose sight of, was very important this time: press conferences were announced all over the world, and the result, an astronomical image,

Sibylle Anderl

Editor in the feuilleton, responsible for the "Nature and Science" department.

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The publication was announced for 3:07 p.m.

Shortly before, a zoom began on our Milky Way, first still in optical view, then flaming orange at infrared wavelengths, revealing the galactic center, deeper and deeper into its strange intricate structures, into the black void where it finally emerged : the first image of Sagittarius A*, the supermassive black hole at the center of the Milky Way.

In the extensive applause of the scientists and press representatives present, not only a few expressed their respect for this significant scientific achievement, but also relief and the feeling that they had finally reached a very important milestone.

Because taking a picture of Sagittarius A*, Sgr A* for short, was the first and actual goal of the scientists from the Event Horizon Telescope (EHT).

Like a tennis ball on the moon

The fact that in 2019 it was nevertheless a different black hole that had been visible in the historical first image of a black hole had practical reasons.

The object shown at that time in the heart of the elliptical galaxy M87 is two thousand times further away than Sgr A*.

But it is more massive by a factor of 1500.

In the sky, both black holes appear to be about the same size - the size of a tennis ball on the moon.

Larger black holes, however, are more permanent and change less rapidly.

This is exactly what made the observation of M87* a significantly easier task compared to Sgr A*.

As soon as this was confirmed in the 1.3 millimeter data from the 2017 measurement campaign, the decision was clear: "Let's do M87 first, develop the methods and show that we can do it," recalls Anton Zensus, founding director of the EHT and Director at the Max Planck Institute for Radio Astronomy in Bonn.

But it was always clear: Sgr A* is the "physics laboratory", the source for which there is so much complementary data that you can work on really interesting research questions.

M87 is also a great galaxy, but the priority has always been Sagittarius A*.

In fact, it was already clearly felt during the press conference and much more in personal discussions with the scientists that Sgr A* is not only physically closer to us.

ESO Director General Xavier Barcons recalled that ESO's core motivation for deploying its telescopes in the southern hemisphere was to study the center of our galaxy.

EHT project director Huib Jan van Langevelde reported how as a student he was fascinated by the "mysterious radio source Sgr A*" and in his own observations he only ever saw blurry images of the center of the Milky Way - between us and the source there is interstellar gas, that scatters radiation and smears images, a second factor besides variability that makes Sgr A* harder to observe compared to M87*.