In April 2019, the world was enchanted, even if only for a moment, by an ominous void surrounded by half a halo of light. Was the first direct image of a black hole; more precisely, a supermassive gravitational abyss in the center of Messier 87, a galaxy in the constellation Virgo, about 54 million light-years from Earth.
Now, a vast international collaboration of scientists has analyzed this data in more detail and, after clearing it of some noise, launched the first polarized image of the black hole, revealing the structure of its magnetic fields.
The research is published today in two papers in the Astrophysical Journal Letters. The papers describe the observational structure of the team and the implications of the findings for understanding the theoretical interpretations of the black hole in the center of M87. The hole is a blazar, which means it has a jet of energy and subatomic particles that drain from the storage disk at almost the speed of light. The characteristics of the jet are defined by the magnetic fields that surround it, so understanding the structure of these fields provides clues to the more enigmatic problem of jet physics.
“If we look at the image now, at the way these polarized vectors behave, then we can deduce the geometry of the magnetic field from it,” said co-author Maciek Wielgus, an astrophysicist at the Center for Astrophysics. Harvard & Smithsonian, in a video call. “It’s extremely interesting for us in terms of jet physics, because we know what we need to have for our theoretical jet ejection models to work.”
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You may find that the new image looks very similar to that original bomb image, but with a little more whirlwind in the storage disk (all things that accumulate around a black hole). However, what describes the new image is a more specific detail of the black hole. The previous view showed total light from the M87 plasmoid nucleus. When a black hole has weak magnetic fields, the plasma draws the fields in a circular pattern, and the light waves oscillate perpendicular to them, as if disturbed by the fields. But when the magnetic fields are strong, the polarized pattern of light waves looks different. And if somewhere between those forces of the field, the emitted polarized light acquires a more spiral shape.
“What this research shows is that the projected image of the M87’s inner accretion flow very close to the black hole appears symmetrical or azimuthal annular,” said co-author Richard Anantua, an astrophysicist at the Center for Astrophysics. Harvard & Smithsonian, in the same video call. “With this structure of the vertical magnetic field, it tells you that magnetic fields don’t just go with the rest of the accumulation flux … magnetic fields are the key scaffold in relativistic jets.”
The Event Horizon telescope is not a traditional telescope at all. It is the unified term for a growing number of observatories spread across four continents, timed to atomic clocks, looking together at space. By efficiently creating a combined telescope the size of the Earth itself, we can dedicate ourselves to a method of cosmological research called very long basic interferometry. The math is complicated, but in essence, the different observers all look at an object and then consider the minimal differences in the arrival of light at each dish to measure the object. As the planet returns, more observatories collect data and can link that data to what has already been recorded. The more data I receive, the clearer the image of a black hole.
In fact, the astrophysicists on this team pulled back the curtain on the black hole’s behavior, as Dorothy and her crew did the Wizard of Oz. However, the difference here is that there are a dozen more behind this curtain. They just improved the wizard’s outline.
Wielgus said that the “holy grail” of the future will be to see better the inner workings of the M87 core; specifically, the larger-scale conditions that formed a huge plasma jet, expelled it, collimated it, and accelerated it. Currently, there is too much noise in the image – and the data behind it – to see something more, such as how an overexposed image can only display the most contrasting objects. With several telescopes in the Event Horizon Telescope range, the team will be able to see how the geometry of the magnetic field changes, changes and shapes the jet emitted from the galactic core.
“It is said that magnetic fields are lazy because they do not work. So magnetic fields, you know, don’t exert magnetic forces that are parallel to them. They exert magnetic forces that are perpendicular to them, “said Anantua. “By the definition of work, if your force is perpendicular to the direction of doing something, do no work. But magnetic fields are actually so lazy that they work around this and only use the black hole to do the job for them. ”
The black hole, far from large nothing, are in fact a stage for a remarkable physics, a place where invisible forces draw longer rays than any distance you have ever known in the cosmos, apparently in defiance of the famous inescapable gravity of the hole.
“This is a magnetic rail weapon,” Maciek said the energy source is the rotational energy of the black hole. ”