The Impossible Photograph

Back in 2019, the Event Horizon Telescope (EHT) produced the first-ever image of a black hole. This event was a first of its kind and it helped to change how to study black holes. The black hole that the EHT took a picture of lies at the center of the M87 galaxy located 55 million light-years from Earth. The image that the EHT captured showed a bright ring around a dark center. That dark center is the black hole’s shadow. While capturing the image, astronomers noticed a large amount of polarized light around the black hole. As part of their next step to learn more about this black hole and other black holes, scientists want to observe the same black hole in polarized light and they just accomplished this goal.

M87 Blackhole's Polarized Light

Polarized light is a different wavelength from unpolarized light. Light is polarized when it's emitted in hot and magnetized areas of space. Because of this, scientists use polarization to determine whether an object has a magnetic field. In this case, there was polarized light sensed and scientists could determine that the black hole’s ring was magnetized. However, at the time, the technology that they had wasn’t powerful enough to see them.

But now they do. To observe the polarized light coming from the black hole, scientists use eight telescopes around the world and combine their power to create a virtual Earth-sized telescope. All the telescopes that are part of the EHT system are radio telescopes that have special receivers that record the sky signal in polarized light. They are similar in how polarized sunglasses work but just on a massive scale.

M87 Blackhole in 2019

By observing the black hole in polarized light, the team of scientists can better understand the event horizon. The event horizon is the boundary where light or other radiation can’t escape. The team of scientists will also study the interaction with the object’s accretion disk. This is a disk of hot gas and other materials that fall into the black hole and swirl around. No matter what scientists are able to learn, the images of the M87 black hole will deepen our understanding of black holes.

The discovery of polarized light helped to confirm the presence of strong magnetic fields in black holes. Astronomers thought that magnetic fields were carried by the hot gas near black holes as an important role in spreading gases into the surrounding galaxy. This is similar to a jet-like stream that spreads these gases throughout the universe. Through more studying and research, scientists hope to learn more about black holes and how they work with respect to the rest of the galaxy and universe. If you want to find out more info about this new discovery, here are 2 papers from The Astrophysical Journal Letter by the EHT. Here is the first paper and here is the second paper.

Sources:

Akiyama, Kazunori, et al. “First M87 Event Horizon Telescope Results. VIII. Magnetic Field Structure near The Event Horizon.” The Astrophysical Journal Letters, vol. 910, no. 1, 2021, doi:10.3847/2041-8213/abe4de. 

Goddi, Ciriaco, et al. “Polarimetric Properties of Event Horizon Telescope Targets from ALMA.” The Astrophysical Journal Letters, vol. 910, no. 1, 2021, doi:10.3847/2041-8213/abee6a. 

Gohd, Chelsea. “First Image of a Black Hole Gets a Polarizing Update That Sheds Light on Magnetic Fields.” Space.com, Space, 24 Mar. 2021, www.space.com/first-black-hole-image-polarized-m87. 

Venom, et al.