The collaboration of the Event Horizon Telescope (EHT), which in 2019 went around the world after taking the first photograph of a black hole, today offers us a new milestone: how the black hole in the center is seen in polarized light of the elliptical galaxy M87 located about 54 million light-years distant from Earth , in the core of the Virgo A subgroup. The galaxy that hosts this black hole is the largest and brightest in the northern part of the Virgo Cluster.
For the first time in the history of astronomical observation, scientists have glimpsed the magnetic fields around a black hole.
Completely new information
As we can see in the image, the EHT has been able to capture the magnetism of the hot and bright gas around the supermassive black hole located at the heart of this galaxy.
The new images reveal unknown details about this dense object, including powerful jets of energy gushing from the center of the supermassive black hole estimated to be about 6.5 billion times the mass of our Sun. They have found that a significant fraction of the surrounding light black hole M87 is polarized.
The researchers measured the polarization near the edge of the black hole, a milestone that will, in turn, allow us to understand the process involved in the production of energetic jets from its core, as these magnetic fields are believed to play a crucial role in the shape in which the black hole engulfs matter and shoots dizzying jets of plasma thousands upon thousands of light-years into space.
Light is a wave that generally moves in all directions and becomes polarized when it passes through certain filters, such as polarized sunglasses lenses, or when it is emitted in warm regions of space where there are magnetic fields. Recall that in the first study of 2019, scientists analyzed visible light and its intensity, but this time, they examined the polarization of that same light that only oscillates in one particular direction.
In nature, interactions between light and matter can influence in this direction, and magnetic fields are among these interactions. Studying polarization is not easy, but it is very important.
“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, which was not possible before ,” explains Iván Martí-Vidal, one of the coordinators of the EHT Polarimetry Working Group. “Unveiling this new polarized light image required years of work due to the complex techniques involved in obtaining and analyzing the data.”
The polarization of the light seen in the M87 image could only be explained by a very strong magnetic field.
“The observations suggest that the magnetic fields at the edge of the black hole are strong enough to push back the hot gas and help it resist the pull of gravity, ” says Jason Dexter of the University of Colorado Boulder. “Only gas that slides through the magnetic field can spiral toward the event horizon.” This finding could help us understand the puzzle of relativistic black hole jets.
What will be next? The researchers hope to be able to publish the first images of Sagittarius A * , the black hole located in the center of the Milky Way, which is 1,000 times closer and 1,000 times smaller than M87, by the end of 2021.
Referencia: 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.
