The latest version of the original image of the supermassive black hole M87 in polarized light. Credit: EHT Collaboration

Scientists Are Working on a Photo of the Milky Way’s Supermassive Black Hole

The second image of a black hole is already on its way.

In the central region of the Milky Way, at a distance of 26 thousand light-years from the Sun, there is a compact radio source known as Sagittarius A*, which is believed to be a supermassive black hole with a mass of 4.2 million solar masses. Astronomers from the Event Horizon Telescope Collaboration are actively working on a photo of that very same black hole, that promises to be historical.

Historical milestone: the first black hole image

In April 2019, the EHT (Event Horizon Telescope) collaboration published the first-ever image of the shadow of a supermassive black hole at the center of the active galaxy M87, located about 55 million light-years from the Sun.

Then, earlier this year, the same team published the first polarized image of the shadow of the same black hole. They were also able to measure the magnetic field strength as well as the average plasma electron density in the emitting region of the supermassive black hole in M87.

EHT close-up of the central region of Galaxy M87 and the shadow of the black hole. Credit: NASA / JPL-Caltech / IPAC
EHT close-up of the central region of Galaxy M87 and the shadow of the black hole. Credit: NASA / JPL-Caltech / IPAC

Now, astronomers are working to obtain an image of the supermassive black hole in the center of the Milky Way – Sagittarius A*. But how does this even work?

When will we see an image of the supermassive black hole in our galaxy – Sagittarius A*?

What we will see will not be exactly the black hole but a region outside the event horizon. That is, it is impossible to see the actual black hole. If it was, we would have already seen hundreds of images of these objects from different galaxies.

Astronomers work towards imaging the “last photon orbit” which is the beam of light that surrounds the supermassive black hole. This is what we saw on the first image of M87 in 2019, and the hole itself is that black shadow in the center.

Photon paths in the vicinity of a black hole. Credit: Nicole R. Fuller / NSF
Photon paths in the vicinity of a black hole. Credit: Nicole R. Fuller / NSF

There is no due date for the image of Sagittarius A*, of course. The original image of M87 already proves that the capabilities of the EHT are limited as most of the details were blurred.

Our expectations should be focused on the next generation EHT which should have higher resolutions and thus, reveal more features and provide a sharper view. They would also be able to capture such images in shorter periods of time.

Photon paths can create multiple layers of light surrounding the black hole. Credit: George Wong (UIUC) and Michael Johnson (CfA)

The main improvement of the next generation EHT will be the ability to reveal more layers of lensed light. As you know already, the light we saw surrounding the M87 black hole comes from the photon ring.

It is important to note that the path of a photon ring can make a full loop around a black hole, thus, creating multiple layers of light. Seeing those layers and understanding them will result in unprecedented data on the gravity and its nature around a black hole.

There is no doubt that the image of M87 was groundbreaking and historical. Having an identical shot of the black hole within our own Milky Way galaxy will be even more significant.

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• Collaboration, T. (2021, March 24). First M87 Event Horizon Telescope Results. VII. Polarization of the Ring.
• Collaboration, T. (2021, March 24). First M87 Event Horizon Telescope Results. VIII. Magnetic Field Structure near The Event Horizon.
The Daily Galaxy. (2021, June 22). “Next Up” –Event Horizon Telescope’s Picture of Milky Way’s Supermassive Black Hole.
Johnson, M. D. (2020, March 1). Universal interferometric signatures of a black hole’s photon ring. Science Advances.
Koberlein, B. (2021, June 4). What Comes After Photographing a Black Hole’s Event Horizon? Could we see the Photon Ring? Universe Today.
Sky & Telescope. (2020, April 6). Scientists Predict Countless Rings of Light Encircle Black Holes.
Tomaswick, A. (2021, June 22). Space Telescopes Could Provide Next-Level Images of Black Hole Event Horizons. Universe Today.

Written by Vladislav Tchakarov

Hello, my name is Vladislav and I am glad to have you here on Curiosmos. As a history student, I have a strong passion for history and science, and the opportunity to research and write in this field on a daily basis is a dream come true.

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