Reacción a "Reactions to the first image of the supermassive black hole at the centre of the Milky Way galaxy"

Black holes do not emit light of their own, but the stars orbiting around them and the matter they devour give us clues about what these giants of the universe are like. We have learned a lot about Sagittarius A*, the black hole at the center of our galaxy, by studying the orbits of stars moving around it. These stars describe very peculiar orbits around... nothing, nothing that we can see or that emits light or other observable radiation. But these orbits can only be explained if we accept that in that region there is an invisible, very compact object with a mass comparable to that of four million suns.

Today the Event Horizon Telescope (EHT) collaboration shows us the first images of the region where these 4 million solar masses are concentrated. As with their previous announcement in April 2019, where they presented the first images of the supermassive black hole in the galaxy M87, what they show us now is also compatible with what Einstein's theory tells us about what black holes should look like. Around a dark spot, from which no light is coming out, we observe a luminous disk of matter at very high energy. It is an accretion disk, something like Saturn's rings but composed of nuclear matter at very high temperature that has been accumulating around the central object (black hole) and is waiting to be devoured at some point. It is thanks to this incandescent matter, which moves at very high speeds attracted by the central object, that we can observe the central dark region corresponding to the black hole.

If of Saturn's rings we can only see the part between the planet and us, because the other part is hidden behind the planet, in the case of Sagittarius A* the intense gravity manages to bend the light rays (and radio waves and X-rays) in such a way that the entire accretion disk is visible, both the part closest to us and the part behind us, as well as the part above and below. The resulting image shows optical effects and deformations that are compatible with what would be expected from the intense gravity generated by an object of 4 million solar masses. Light can be bent by gravity and the images show that bending at its best.

To observe for the first time the image of the glowing masses orbiting in the regions closest to the black hole of our own galaxy, the Milky Way, is a luxury that history has reserved for us. This is a great example of what humanity can achieve by working together in peace and harmony. It takes great ingenuity to use an array of eight isolated antennas distributed around the planet to combine their signals and produce the equivalent of what an antenna the size of planet Earth would observe. Once this historic milestone has been reached, it is necessary to be even more daring, careful and patient to accumulate enough data to reconstruct the image that we have been able to contemplate today.

Beyond their artistic quality, since we are all excited to observe an incandescent plasma that will be devoured by a supermassive black hole, these images contain valuable scientific information that will help us to better understand the properties of matter under extreme conditions of pressure and temperature. We will also be able to test our physical theories about matter and gravity, because it is one thing if what we see looks like what we expect, and another if it is exactly that. Precision science is fundamental to advancing knowledge. Having the courage to risk initiating explorations of this caliber is within the reach of only a few. The EHT collaboration is the result of a bold combination of risky ideas and precision work of the highest level, implemented by some 300 people working side by side, day and night, for years.

The images brought to us today by the EHT are strikingly similar to the one they showed in 2019 of the black hole in the supermassive galaxy M87. Although that object is about a thousand times larger than the one observed today in the Milky Way, its resemblance to our 'little' black hole shows the universality of the physical principles describing these objects.