2023-05-01 19:32:52
M87* is the supermassive black hole at the heart of the giant galaxy M87 which provided the first image of the shadow of the event horizon of these compact stars. Today, a group of radio telescopes including those of Alma, ESO, reveals in a single image the same black hole, but also the birth of its jet of matter from a ring of matter around M87 * . This is enough to better understand the other jets of black holes.
Already in April 2019, the galaxygalaxy Messier 87 (M87M87), an enormous elliptical galaxyelliptical galaxy located regarding 55 millionlight yearslight years of the Earth, hit the headlines in the field of radio astronomy. In fact, the astronomersastronomers studied it for centuries in the visible and in the constellation of Virgo, following its discovery by Charles MessierCharles Messier in 1781. It was later realized that in addition to containing 10 times morestarsstars that Milky WayMilky Wayshe also contained in her heart a supermassive black holesupermassive black hole which was an excellent target to be able to observe the shadow of theevent horizonevent horizon of a black hole.
For this, it was necessary to mobilize observations from several radiotélescopesradiotélescopes on the surface of the Earth and implement with them the technique of opening summaryopening summary. It makes it possible to virtually have a radio telescope the size of the Earth by combining the observations of these instruments and therefore being able to produce images with a resolutionresolution record.
Roger Blandford tells us regarding supermassive black holes and their jets in this video. To obtain a fairly accurate French translation, click on the white rectangle at the bottom right. The English subtitles should then appear. Then click on the nut to the right of the rectangle, then on “Subtitles” and finally on “Translate automatically”. Choose “French”. © Quanta Magazine
Additional observations from the EHT
This is what the members of the collaboration had succeeded in doing Event Horizon Telescope (EHT), thus revealing, in 2019, the first image of a black hole. Today, as explained in a press release from the European Southern Observatory (ESO) which accompanies a publication in Naturewe observed for the first time on the same image, the shadow of the black hole in the center of M87) and the powerful jet of particles of mattermatter almost going to speed of lightspeed of light who is expelled.
The press release also specifies that it is the result of a long-term process of processing the signals collected because it began with observations made in 2018 with the telescopestelescopes of Global Millimetre VLBI Array (GMVA), of theAtacama Large Millimeter/subimeter Array (Alma) and Greenland Telescope (GLT).
This jet has been known for a long time since the American astronomer Heber Doust Curtis had observed it as early as 1918. But it was only later that we would understand that this particularly fine and collimated jet of matter, extending over at least 5,000 light-years away, is the result of complex physical processes relating to the magnetohydrodynamics of plasmas in space-timespace-time curve, in this case that of a Kerr black holeKerr black hole in rotation containing approximately 6.5 billion massesmasses solar, as Futura explained at length in a previous article.
A laboratory to understand the astrophysics of galactic black holes
The challenge of the new analyzes of the observations is broader than the case of M87 because several similar jets are known and we know that they must be related to the interactions between the supermassive black holes and the galaxies which shelter them.
« We know that jets are ejected from the region around black holes, but we don’t yet fully understand how this happens. To study it directly, we must observe the origin of the jet as close as possible to the black hole. “Explains in the statement of the ESO Ru-Sen Lu, of the Astronomical Observatory of Shanghai, in China.
Previous observations had provided separate images of the region near the black hole and the jet, but ” this new image completes the picture by showing the region around the black hole and the jet at the same time », adds his colleague Jae-Young Kim from Kyungpook National University in South Korea and the Max-Planck Institute for Radio Astronomy in Germany.
A summary of the discovery made with Alma. To obtain a fairly accurate French translation, click on the white rectangle at the bottom right. The English subtitles should then appear. Then click on the nut to the right of the rectangle, then on “Subtitles” and finally on “Translate automatically”. Choose “French”. © European Southern Observatory (THAT)
Still in the same press release, we learn that the gain in resolution still obtained in the case of M87 comes from the fact that the researchers with the radio telescopes used have taken advantage of waves radioradio with a longer wavelength than that of the EHT: 3.5 mm instead of 1.3 mm. As Thomas Krichbaum of the Max-Planck Institute for Radio Astronomy explains, ” at this wavelength we can see how the jet emerges from the emission ring around the central supermassive black hole “. The size of the observed ring is regarding 50% larger than that of the image of theEvent Horizon Telescope.
« To understand the physical origin of this larger and thicker ring, we had to use computer simulationscomputer simulations to test different scenarios », and ajoute Keiichi Asada de l’Academia Sinica in Taiwan.
Ultimately, the image would more fully show some of the material falling toward the supermassive black hole’s event horizon.
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