A new image of a black hole reveals its mysterious physics

Two years ago, The Event Horizon Telescope (EHT) made headlines with the announcement of the first vertical image of a black hole. The journal Science named the image as Breakthrough of the Year. Now the EHT collaboration is back with another innovative product: a new image of the same black hole, this time showing how it looks in polarized light. The ability to measure this polarization for the first time – a signature of magnetic fields at the edge of the black hole – is expected to provide a new perspective on how black holes build up and allow -power powerful jets from their rights. The new findings were reported in three papers published in Letters of the Astrophysical Journal.

“This work is a major milestone: Light polarization carries information that allows us to better understand the physics behind the image we saw in April 2019, which was not possible before, said coauthor Iván Martí-Vidal, EHT Polarimetry Coordinator working group and researcher at the University of Valencia, Spain. “The publication of this new polarized light image required years of work due to the complex methods involved in obtaining and analyzing the data.”

Image Multiplexing produced the first ever vertical image taken of a black hole in the center of an elliptical galaxy. Located in the constellation Virgo, about 55 million light-years away, the constellation is called Messier 87 (M87). The results of the collaboration were published on April 10, 2019, in six separate papers appearing there Letters of the Astrophysical Journal. It is an action that would have been impossible a generation ago, made possible by technological advances, innovative new algorithms, and of course, connecting several of the best radio stations in the world. world. The image confirmed that the object in the middle of the M87 is a black hole.

The EHT captured locked photons in orbit around the black hole, orbiting at the speed of light, creating a bright ring around it. From this, astronomers were able to detect that the black hole is spinning clockwise. The image also revealed the shadow of the black hole, a dark area in the center inside the ring. That shadow is as close as astronauts can get to photographing the real black hole, from which light cannot escape when it crosses the horizon of the event. And just as the magnitude of the event horizon is proportional to the mass of the black hole, so too is the shadow of the black hole: The larger the black hole, the greater the shadow. (The mass of the black hole of the M87 is 6.5 billion times larger than our sun.) It was a remarkable testament to a general theory of relevance, showing that these predictions hold up even in harsh gravitational environments.

However, what was missing was a look at the process behind the powerful jets of pairs that made the black hole build up, sending out a portion of the material falling into it at a speed not. very light. (The black hole in the middle of our Milky Way is less ravenous, ie, relatively quiet, compared to the black hole of the M87.) For example, astronomers still do not agree on how to accelerate these jets. to such a high speed. These new results place additional constraints around the various competing theories, narrowing the possibilities.

In the same way that polarized sunglasses reduce glare from a clear surface, the polarized light around a black hole provides a sharper view of the surrounding area. In this case, the polarization of light is not due to specific filters (like the lenses in sunglasses) but the presence of magnetic fields in the hot spot around the black hole. That polarization allows astronomers to map magnetic fields at the inner edge and study the interaction between subject flowing in and being blown out.

“The observations indicate that the magnetic fields at the edge of the black hole are strong enough to push back on the hot gas and help it resist gravity attraction. It is just the gas that slides. through the field that can weave into the horizon of the event, ”said coauthor Jason Dexter of the University of Colorado, Boulder, who is also the coordinator of the EHT Theory Working Group. That means that only theoretical models that incorporate a gas feature with strong magnetization accurately describe what the EHT collaboration has observed.

This story first appeared Ars Technica.

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