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New image in polarized light of the black hole of the galaxy M87

The scientific collaboration of Event Horizon Telescope (EHT which in 2019 allowed the first image of a black hole to be obtained, today revealed a new perspective of the massive object at the center of the planet. galaxy M87: how it looks in polarized light.

This is the first time that astronomers have been able to measure polarization, the ‘signature’ of magnetic fields, so close to the edge of a black hole. The observations are key to explaining how the galaxy M87, located at 55 million light years away, it can launch very energetic jets of material from its core.

For the first time, astronomers have been able to measure polarization, the ‘signature’ of magnetic fields, so close to the edge of a black hole – key observations to explain how the galaxy M87 shoots jets of material

“We are facing unique evidence to understand how magnetic fields behave around black holes, and how activity in this very compact region of space can drive powerful jets that extend far beyond the galaxy,” he says. Monika Mościbrodzka, Coordinator of the EHT Polarimetry Working Group and Assistant Professor at Radboud University (The Netherlands).

The first image of the black hole released on April 10 two years ago revealed a bright ring-shaped structure with a dark central region – the hole’s shadow. Since then, the EHT collaboration has delved into data on the supermassive object at the heart of the galaxy M87 collected in 2017 and found that a significant fraction of the light around the black hole M87 is polarized.

An important milestone

“This work is an important milestone: the polarization of light carries information that allows us to better understand the physics behind the image we saw in April 2019, something that was not possible before,” he explains. Iván Martí-Vidal, also coordinator of the EHT polarimetry working group and researcher of the GenT program at the University of Valencia–. Developing this new image in polarized light has required years of work due to the complex techniques involved in obtaining and analyzing the data. “

The polarization of light carries information that allows us to better understand the physics behind the famous image we saw in 2019, something that was not possible before

Iván Martí-Vidal (UV)

Light becomes polarized when it passes through certain filters, such as polarized sunglasses lenses, or when it is emitted in hot, magnetized regions of space. In the same way that polarized sunglasses only allow a certain orientation of the electric field of the Sun’s rays to pass through, astronomers can obtain information about the orientation of the electric field of light coming from space using polarizers installed in telescopes. . Specifically, polarization makes it possible to map the magnetic field lines present at the inner edge of the black hole.

“The recently published polarized images are key to understanding how the magnetic field allows the black hole to gobble up matter and launch powerful jets,” he says. Andrew Chael, member of the EHT collaboration and researcher at the Princeton Center for Theoretical Science (USA).

Luminous jets of energy and matter

The bright jets of energy and matter that emerge from the core of M87 and extend at least five thousand light-years from its center are one of the most mysterious and energetic features of the galaxy. Most of the matter near the edge of a black hole falls into it. However, some of the surrounding particles escape moments before capture and are expelled into space in the form of jets.

The bright jets of energy and matter that emerge from the core of M87 and extend at least five thousand light-years from its center are one of the most mysterious and energetic features of the galaxy.

The team has relied on different models of how matter behaves near the black hole to better understand this process. But they still don’t know exactly how jets larger than the galaxy itself are propelled from its central region, as small in size as the Solar System, or how matter falls into the black hole. With the new EHT image of the black hole, astronomers have for the first time glimpsed the boundary region of the black hole where this interaction occurs between matter that flows in and that which is expelled.

Observations explained by theories

The observations provide new information about the structure of the magnetic fields at the edge of the black hole. The team found that only theoretical models with strongly magnetized gas can explain what they are seeing on the event horizon.

Some of the material that does not fall into the black hole is carried away by the magnetic field, giving rise to the powerful jets that we observe for the first time in the active nuclei of galaxies like M87.

José Luis Gómez (IAA-CSIC)

“The observations suggest that the magnetic fields at the edge of the black hole are strong enough to retain the hot gas and help it resist the pull of gravity. Only the gas that slides through the field can spiral towards the event horizon ”, explains Jason Dexter, assistant professor at the University of Colorado at Boulder (USA) and coordinator of the EHT theory working group.

“Part of the surrounding material that does not fall into the black hole is dragged by the magnetic field giving rise to the powerful jets that we observe in the active nuclei of galaxies, such as M87, something that we had not been able to observe until now,” he says. Jose Luis Gomez, coordinator of the EHT mapping work group and leader of the EHT group at the Institute of Astrophysics of Andalusia (IAA-CSIC), which also includes researchers Rocco Lico, Guang-Yao Zhao, Antonio Fuentes, and Antxon Alberdi . “Multiple analysis techniques of the EHT data have been used to corroborate these results that allow us to restrict the physics that produce and feed these extreme objects,” adds Lico.

Union of 8 telescopes and 300 researchers

To observe the heart of the M87 galaxy, the collaboration linked eight telescopes from around the world, including the IRAM radio telescope of 30 meters in Pico Veleta (Sierra Nevada), to create a virtual telescope the size of the Earth, the EHT. The impressive resolution obtained with the EHT is equivalent to that required to measure the length of a credit card on the surface of the Moon.

The impressive resolution obtained with the EHT is equivalent to that required to measure the length of a credit card on the surface of the Moon.

This allowed the team to directly observe the black hole’s shadow and the ring of light around it, with the new polarized light image clearly showing that the ring is magnetized. The results are published today in two separate articles in The Astrophysical Journal Letters signed by the EHT collaboration. The research involved more than three hundred researchers from multiple organizations and universities around the world.

“The EHT is moving fast, with technological updates being made in the various telescopes that make up the EHT, including the addition of new observatories. We hope that future EHT observations will more accurately reveal the structure of the magnetic field around the black hole and tell us more about the physics of hot gas in this region, “he concludes Jongho Park, a member of the EHT collaboration and a researcher at Academia Sinica (Taipei Institute of Astronomy and Astrophysics, Taiwan).

Location of the participating telescopes of the Event Horizon Telescope (EHT) and the Global mm-VLBI Array (GMVA). / ESO / O. Furtak

References:

First M87 Event Horizon Telescope Results. VII: Polarization of the Ring / VIII: Magnetic Field Structure near The Event Horizon / Goddi, Martí-Vidal, Messias, and the EHT Collaboration: Polarimetric properties of Event Horizon Telescope targets from ALMA. ApJL, 2021.

Rights: Creative Commons.

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