First historical image of the black hole

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And team group of researchers has captured the first image view of Sagittarius A*, the supermassive black hole at the center of the Milky Way. This result constitutes overwhelming evidence that the object is indeed a black hole and provides valuable clues regarding the workings of these giants, which are believed to reside at the center of most galaxies.

Historical image of the black hole

The image has been obtained by a global research team, the Event Horizon Telescope Collaboration. Event Horizon Telescope, EHT), using observations with a global network of radio telescopes, which functions as a virtual telescope the size of the Earth. The results of the EHT team were published last Thursday, May 12, in a special edition of The Astrophysical Journal Letters.

The image represents a long-awaited glimpse of the huge object that sits at the center of our galaxy. Previous research had detected stars orbiting an invisible, compact and very massive object at the center of the Milky Way, suggesting that this object – known as Sagittarius A* (named Sagittarius A star or Sgr A*)– is a black hole. The image released today provides the first direct visual evidence of this.

Although we cannot see the black hole itself, since it is a completely dark object, the glowing gas that surrounds it shows a telltale signature: a dark central region (called sombra) surrounded by a bright ring-shaped structure. This new view captures light bent by the powerful gravity of the black hole, which has a mass four million times that of the Sun.

The size of the black hole ring matches the predictions of the Theory of Relativity

“We were surprised by how well the ring size matched the predictions of Einstein’s Theory of General Relativity”says the principal scientist of the EHT project Geoffrey Bowerfrom the Institute of Astronomy and Astrophysics, Academia Sinica (Taipei). “These unprecedented observations have greatly improved our understanding of what is happening at the center of our galaxy and offer new insights into how giant black holes interact with their surroundings.”.

Because the black hole is regarding 27,000 light-years from Earth, from our perspective its size in the sky is regarding the size of a donut on the Moon. To obtain the image, the team used the powerful Event Horizon Telescope (EHT), which joined eight radio telescopes distributed across the entire planet to form a single virtual telescope the size of Earth.

The EHT observed Sgr A* several nights, collecting data for many hours at a time, similar to using a long exposure time on a still camera. Among the radio telescopes that make up the EHT, the thirty-meter IRAM antenna located in Sierra Nevada (Granada) has played an essential role in the observations that have made it possible to obtain the first image of the black hole in SgrA*. This new milestone continues the path of the EHT collaboration, which in 2019 spread the first image of a black hole, M87*located in the center of the most distant galaxy: Messier 87.

The black hole in our galaxy is much smaller and less massive.

The two black holes look remarkably similar, even though the black hole in our galaxy is more than a thousand times smaller and less massive than M87*.

“We have two completely different types of galaxies and two very different masses of black holes, but near the edge of these black holes they look amazingly similar.” –point Sera Markoff, co-chair of the Scientific Council of the EHT and professor of theoretical astrophysics at the University of Amsterdam–. This tells us that General Relativity rules these objects up close, and any differences we see further away are due to differences in the material surrounding the black holes.”.

This result was considerably more difficult than that of M87*, even though Sgr A* is much closer. The EHT Scientist Chi-kwan Chan, of the Steward Observatory and the Department of Astronomy and the Data Science Institute of the University of Arizona (USA), explains:

“Gas in the vicinity of black holes moves at the same speed -almost as fast as light- around Sgr A* and around M87*. But while the gas takes days to weeks to orbit the larger M87*, the much smaller Sgr A* completes an orbit in a matter of minutes. This means that the brightness and pattern of the gas around Sgr A* was changing rapidly as the EHT Collaboration observed it: it was a bit like trying to take a clear picture of a puppy rapidly chasing its tail.”.

New observation tools

The team had to develop sophisticated new tools to account for gas movement around Sgr A*. While the M87* was an easier and more stable lens, in which almost all images looked the same, that was not the case with the Sgr A*. The Sgr A* black hole image is an average of the different images the team extracted, finally revealing the giant that resides at the center of our galaxy for the first time.

The effort has been made possible through the ingenuity of the team of more than 300 people from 80 institutes around the world that make up the EHT collaboration. In addition to developing complex tools to overcome the challenges of obtaining the first image of Sgr A*, the team worked rigorously for five years, using supercomputers to combine and analyze their data, all while compiling an unprecedented library of simulated black holes. to compare with observations.

“Previous studies, awarded the Nobel Prize in Physics in 2020, had shown that an extremely compact object with a mass four million times greater than our Sun resides at the center of our galaxy. Now, thanks to the EHT, we have been able to obtain the first visual confirmation that this object is almost certainly a black hole with properties that are in perfect agreement with Einstein’s Theory of General Relativity.”says Jose Luis Gomez, member of the Scientific Council of the EHT and leader of the EHT group at the Institute of Astrophysics of Andalusia (IAA-CSIC). Research with the EHT is a fundamental part of the Severo Ochoa strategic project of the IAA-CSIC.

collaboration

The collaboration is excited to finally have images of two black holes of vastly different sizes, offering an opportunity to understand how they compare and contrast. They have also begun to use the new data to test theories and models regarding how the gas around supermassive black holes behaves, a process not yet fully understood but believed to play a key role in their formation and evolution. of the galaxies.

“Now we can study the differences between these two supermassive black holes to gain valuable new clues regarding how this process works.”points out the EHT scientist Keiichi Asada from the Institute of Astronomy and Astrophysics, Academia Sinica (Taipei). ‘We have images of two black holes, one at the big end and one at the small end of the supermassive black holes that populate the universe. So we can go further than ever before to analyze how gravity behaves in these extreme environments.”.

Advances in the EHT continue: in March 2022, a large observing campaign was developed that included more telescopes than ever before. The continued expansion of the EHT network and major technology upgrades will enable the collaboration to share even more impressive images and movies of black holes in the near future.

Spain has made an essential contribution

Spain has had an essential contribution to the results presented in the EHT. The Institute of Astrophysics of Andalusia (IAA-CSIC) has co-led the necessary work at an international level to obtain the first image of the black hole in SgrA*, while the University of Valencia (UV) has carried out a very important part from the analysis of the EHT data.

The Spanish team that has participated in this finding is made up of researchers Jose Luis Gomez, Antonio Fuentes, Rocco Lico, Guang-Yao Zhao, Ilje Cho, Thalia Traianou, y Antxon Alberdi at the IAA-CSIC; Iván Martí Vidal, Alejandro Mus, y Rebecca Azulayof the UV; Miguel Sánchez Portal, Salvador Sánchez, Pablo Torné, Ignacio Ruiz, Santiago Navarro Fuentes, e John Myserlis of IRAM.

Fuente: IAA-CSIC Communication

Reference article: https://www.csic.es/es/actualidad-del-csic/captada-la-primera-imagen-historica-del-agujero-negro-del-centro-de-la-galaxia