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The goals of science are constantly evolving, as each new discovery is the introduction to a succession of other discoveries in our quest to understand the universe, and the supermassive black hole M87 * is no exception.
And this black hole is the subject of humanity’s first direct image of the shadow of a black hole, in a very astonishing feat for many years.
Now, scientists have teamed up with the Event Horizon Telescope to analyze this glowing ring of golden light 55 million light years away and have found evidence of strong polarization – the twisting of light waves, generated by strong magnetic fields. from the surrounding area. the black hole.
Astronomer Evan Marty Vidal, from the University of Valencia in Spain, said: “This work is a major step: the polarization of light carries information that allows us to better understand the physics behind the image we have. seen in April 2019, which was not the case. possible before. The new polarized light has years of work, due to the complex techniques involved in acquiring and analyzing data. “
Polarization is a well known and understood behavior of electromagnetic radiation. When a particle of light passes through space, its vibrations are directed in a specific direction. If it is scattered, for example, in the middle between two stars, or is rotated by a magnetic field, its direction may change; We call this the polarization of change.
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It’s a feature that we can technically use – you might have heard of polarized screen protectors and sunglasses – but it can also, when emitting cosmic objects, tell us something about the environment in space.
For M87 *, this thing is the shape and structure of the magnetic field in the gas field that orbits directly around the outer event horizon of the black hole. The team found that the polarization of visible light in the M87 * image could only be explained by a very strong magnetic field.
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Astronomer Jason Dexter, of the University of Colorado at Boulder, said: “Observations indicate that magnetic fields at the edge of the black hole are strong enough to repel hot gas, helping it resist gravitational pull. . ”.
This can be essential in understanding a phenomenon that has long been a puzzle: relativistic black hole jets.
Nothing that we can currently discover can escape the black hole once it crosses the critical proximity threshold, but not all of the accretion disc material hovering in the energetic black hole inevitably ends well beyond it. of the event horizon. Somehow, a small portion of it is directed from inside the accretion disk toward the poles, where it is pushed out into space as jets of ionized plasma, to a speed less than the speed of light.
Astronomers believe that the magnetic field of a black hole plays a role in this process. And the magnetic field lines, according to this theory, act like a “synchrotron” that accelerates the material before it is released at tremendous speed.
And we know the M87 * shoots these relativistic jets at 99% the speed of light. The shiny gold ring, which we can see in the image of the M87 *, is the inner edge of the accretion disc, giving scientists a unique window into the process.
“We now see the next important piece of evidence to understand how magnetic fields behave around black holes, and how activity in this very compact region of space can lead to powerful jets that expand into what is, ”said astronomer Monica Moisbrodzka from the University. from Radboud in the Netherlands. Beyond the Galaxy. “
The researchers said the observed magnetic field structure could produce all of the observed features of the M87 * ring, as well as the powerful relativistic jets it launches into space. They are among the best evidence to date that supports the synchrotron magnetic field model of relativistic jet formation.
The team said future analysis will focus on magnetic fields around the firing area near the M87 * event horizon.
The research is published in The Astrophysical Journal Letters via these links: 1 and 2.
Source: ScienceAlert
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