A new portrait of the most famous of black holes

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Two years ago, the Event Horizon Telescope collaboration revealed to us the incredible very first image of the shadow of a black hole. These same researchers have just published a new portrait of the object, revealing new details related to its magnetic field.

M87 is a black hole 6.5 billion times more massive than the sun found in the center of a huge elliptical galaxy about 55 million light years from Earth in the constellation Virgo. Two years ago, an international team of researchers offered us the very first image of this black hole, revealing a fuzzy “smoke ring”, just as Albert Einstein’s equations predicted a century ago. .

This same group has spent the past two years extracting more data from their observations. For this work, they focused on the polarization of waves capable of revealing the shape of the magnetic fields found in the hot gas swirling around the object.

A new portrait in polarized light of a black hole

Light is a wave that generally “trembles” in all directions. Polarized light waves are light waves whose vibrations occur on a single plane. Light becomes polarized when it passes through certain filters, such as sunglasses, for example, but also when it is emitted by hot regions of space where magnetic fields reside. Polarized, light only oscillates in a particular direction. In nature, interactions between light and matter can influence this direction, and magnetic fields are one of these interactions.

Seen through the radio equivalent of polarized sunglasses, M87 appears to us today as a vortex pumping interstellar matter.

The newly processed image allows astronomers to trace these fields back to their origins, in a hot and chaotic ring of plasma fromabout 30 billion kilometers in diameter (four times wider than Pluto’s orbit).

An image of the M87 black hole revealing what it looks like in polarized light. The lines mark the orientation of the polarization related to the magnetic field around the shadow of the black hole. Credits: EHT Collaboration

Learn more about relativistic jets

Thanks to this new portrait, researchers are thus giving themselves the means to study its magnetic field. These observations can in turn help astronomers to understand how phenomena such as cosmic jets are formed.

Black holes are real pits found here and there capable of anything and everything. Paradoxically, these objects are also the brightest in the universe. Material that falls into a black hole is heated as it swirls around the drain. Most of this material falls into the black hole, but some is expelled. Astronomers do not know how all this energy arises and is mobilized, hence the importance of this new portrait.

These relativistic jets are some of nature’s most extreme phenomena, combining gravity and hot gases and magnetic fields to produce a beam that passes through a galaxy“, Recalls Daniel Holz of the University of Chicago. “It’s exciting that EHT is helping us find out more about what goes on at the heart of these jets which, we know, take root very close to the “surface” of a black hole.“.

Janna Levin, an astrophysicist at Barnard College of Columbia University, also called the results “exciting“. And for good reason, we finally have details on how black holes can create “Ray guns spanning thousands of light years“.

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Part of the Messier 87 jet (6000 light years long) shown in polarized light. Credit: ALMA

Incidentally, this work has also enabled astronomers toestimate the speed at which this black hole feeds on its environment. Apparently he is not terribly hungry; the black hole eats a “paltry” thousandth of the sun’s mass per year. Yet it is enough to project relativistic jets spanning thousands of light years, and bright enough that we can observe them.

Details of this work are published in The Astrophysical Journal here and here.

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