Did Event Horizon Telescope film the supermassive black hole in the Milky Way Sgr A *?

We remember that on Wednesday, April 10, 2019, at 15.00 in France,the international teamEvent Horizon Telescope (EHT) led by Shep Doeleman, researcher at the Center forastrophysics Harvard-Smithsonian, had made headlines by publishing the historical image of the supposed supermassive black hole M87 *. It is located in the center of the great elliptical galaxy M87 is about 53 millionlight years of the Milky Way.

We also expected to see the picture of supermassive black hole just as supposed in the heart of our galaxy. With some masses 4.3 million and 6 to 7 billion solar masses (M87 *), respectively, the theory of general theory of relativity predicts for these stars event horizon sizes of 25 million and 36 billion kilometers, respectively. Considering the distance to Earth, these compact objects have similar apparent diameters, which are of the order of an apple or a golf ball observed from Earth on the surface of Moon.

Jean-Pierre Luminet, Research Director at CNRS, and Françoise Combes, Professor at the Collège de France, talk to us about black holes, especially in the large supermassive black holes in galaxies that lie behind quasars and that affect galaxy evolution. © Hugot Foundation at the College de France

Let us keep in mind that the only thing that defines a black hole is the ability to identify the boundaries of a virtual enclosed surface that surrounds an area ofspace time which one cannot escape without being able to exceed speed of lightwhat physical known prohibited. L ‘the state of matter and space-time below the surface inside a black hole is unknown, and although the theory of relativity alone implies the occurrence of a singularity in the core of the black hole, where the curvature of space-time is infinite and the density of fabric just as much (as demonstrated by the Nobel Prize in Physics Roger Penrose ), we do not know. Actually, the laws of quantum mechanics, such as Heisenberg and Schrödinger has revealed to us, and which describes what is called space foamstrongly suggests that nothing like this is likely to happen.

Finally, it may well be that the objects we take for black holes in fact, stars are almost as compact and thus behave in many respects as black holes from an astrophysical point of view, but without event horizon genuine, thus not black holes, as Hawking himself had imagined. It could be super-string ballsof tombstones and even off wormholes !

This Wednesday, April 10, 2019, there is unfortunately no picture of the Milky Way’s supermassive black hole connected to the famous spring radio Sagittarius A * (Sgr A * for short), had not been displayed because data collected by the international network of radio telescopes makes it possible to get a virtual instrument almost the size of the Earth to obtain the power from solution necessary for the observations had proved to be more difficult to deal with than expected. However, the researchers in the EHT collaboration continued to both take new data and improve their treatment.

Needless to say, for more than a week now, tensions have been rising following an announcement promising us news of Sgr A *.

It was a joint press release from European Southern Observatory (ESO) andEvent Horizon Telescope (EHT) explains that on May 12, 2022 thanks global village and WWWthere will be an online conference on this topic, which can be followed live from kl. 15.00 in France.

The conference on May 12, 2022 live. © European Southern Observatory (ESO)

As a prelude to this conference and to try to imagine its content, let’s remember what Shep Doeleman explained to AFP in 2019 “For years I told people we would get a picture of a black hole and they told me they would believe me when they saw it. The scientific community expressed some skepticism, which is normal. When you finally get the proof, when you achieve such a breakthrough, you really feel the satisfaction of having given birth to a new field of research.he continues. We are now in an era of high-precision images of black holes. We can make space-time maps for the first time “. Better, according toastrophysicistalready at that time his colleagues were working on producing a video from the mountains of recorded data. “By the end of the next decade, we will be making high-quality real-time films of black holes that will reveal not only their appearance but also their behavior on the cosmic scene.”assured Shep Doeleman.

He also explained that it is precisely because of the very dynamic and turbulent accumulation of matter on the central black hole in the Milky Way that we did not yet have a picture of Sgr A *. But it also means very precisely that one must obtain images that show a clear development over time. “It takes about a month for the case to circulate around M87 *. But for Sagittarius A * it only takes half an hour. On a night’s observation, Sgr A * can change in front of us”, he added and also explained: “It is possible that we are making a rather raw first film. Ideally more than telescopeson the ground or inside orbit earthly, to increase the resolution. But we will refine this over time. It may be like the first movies in the cinema “.

Finally, remember that it is the French astrophysicist and cosmologist Jean Pierre Luminetas he explained several times and with many details about the versions French and English of blog which Futura made available to him, which was the first in the late 1970s to count on computer the visual appearance of a black hole surrounded by one accretion disk. With his colleague Jean-Alain Marck, he then performed simulations that showed the appearance of such an object from several angles, and we can therefore believe that we will be able to make comparisons between M87 * and Sgr A *, which should not be presented below same orientation eyes of the noosphere.

A numerical simulation based on calculations in general relativity of the appearance of a black hole surrounded by a hot growth disk. It was made by astrophysicist Jean-Alain Marck in 1991. Excerpt from the documentary “Infiniment curved”. To get a fairly accurate French translation, click on the white rectangle at the bottom right. The English subtitles were then to appear. Then click on the nut to the right of the rectangle, then on “Subtitles” and finally on “Automatically translate”. Select “French”. © Authors: Laure Delesalle, Marc Lachieze-Rey, Jean Pierre Luminet. Instructor: Laure Delesalle. Production: CNRS / Arte, France (1994)

The members of the EHT collaboration could therefore tomorrow surprise us with breathtaking pictures of Sgr A *. We can also reasonably expect new constraints for new physics that could replace the theory of relativityEinstein and of course also about the existence or not of an event horizon.

Einstein’s general theory of relativity is in fact not the only possible one that is compatible with the theory of Relativity and based on the possibility of space-time curvature. From equations different are reduced to Einsteins in certain situations, just as was the case for the equations for Newton which is the borderline case of Einstein, is considered and studied for more than 50 years as the famous tensor-scalar theories.

To invalidate Einstein’s theory in favor of these variants can give us keys to solving the riddles related to black fabric anddark energy. Conversely, supermassive black holes are thought to have an outer space-time geometry that is one rotating Kerr black hole. This involves movements very precise for matter and paths that are just as precise for the light rays produced by the heated substance from a growth disk around certain black holes.

If the agreement is good enough between the predictions in Einstein’s theory of a Kerr black hole and the new observations made by the members of the EHT collaboration, then it may lead to the rejection of exotic and rather incredible alternatives to the theory of black holes.

One can get an idea of ​​how the observations of Sgr A * can lead to exploration of alternative theories to Einstein and to the solutions of their equations describing alternatives to Einstein’s general theory of relativity, by consulting the video below, which already talked about these tests performed with EHT, but for M87 *.

We can estimate the mass of the black hole M87 * by studying the motions of the stars around it. A solution of Einstein’s equations with the mass of M87 * implies a given image and size for the shadow of a black hole event horizon. Alternative theories of gravity plus exotic kinds of electric charges involve different images with smaller event horizon sizes, as this video explains. EHT therefore makes it possible to test new theories about gravity and the existence of exotic black holes. To get a fairly accurate French translation, click on the white rectangle at the bottom right. The English subtitles were then to appear. Then click on the nut to the right of the rectangle, then on “Subtitles” and finally on “Automatically translate”. Select “French”. © BlackHoleCam

To refresh your memory about EHT’s global network of radio telescopes and what it can observe for the so-called shadow (shade, in English) of a black hole, you can watch the video below.

A long presentation of the discovery made withEvent Horizon Telescope in 2019. To get a fairly accurate French translation, click on the white rectangle at the bottom right. The English subtitles were then to appear. Then click on the nut to the right of the rectangle, then on “Subtitles” and finally on “Automatically translate”. Select “French”. © European Southern Observatory (ESO)

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