Peter Lobner, 25 March 2021

The first image of the shadow of a black hole was released on 10 April 2019 by the Event Horizon Telescope (EHT) collaboration and the National Science Foundation (NSF).  The target of their observation was the supermassive black hole located near the center of the Messier 87 (M87) galaxy, which is about 55 million light years from Earth.  That black hole is estimated to have a mass 6.5 billion times greater than our Sun.

After further analysis of the historic M87 data, EHT astronomers have been able to measure the polarization of the radio frequency signals from the bright disk of the black hole.  Polarization is a signature of the direction of the very strong magnetic fields in the hot glowing gas at the edge of a black hole, which can be seen in the following image released on 24 March 2021.  

The ability to measure the polarization in fine detail provides a new tool for mapping the dynamic magnetic field structure of a black hole.  The new image shows the magnetic fields in the swirling accretion disk, which contains matter that is falling into the black hole.  

Researchers also measured polarization that is pointing directly toward or away from the black hole, perpendicular to the accretion disk.  Very strong magnetic fields in these directions may be responsible for launching plasma jets into space, away from the black hole.  Such jets have been observed emanating from some black holes.

These are exciting times in astronomy and astrophysics.

For more information:

• Maria Temming, “A new black hole image reveals the behemoth’s magnetic fields,” ScienceNews, 24 March 2021: https://www.sciencenews.org/article/black-hole-picture-magnetic-fields-event-horizon-telescope
• Chelsea Gohd, “First image of a black hole gets a polarizing update that sheds light on magnetic fields,” Space.com, 24 March 2021: https://www.space.com/first-black-hole-image-polarized-m87