‘Black Hole Hunter’: What is the Horizon Telescope of the Event and what are the key steps in its investigation? | Science

On Thursday (12), scientists from the international community released the image for the first time Sagittarius A *a very large black hole living in the middle of our Milky Way.

Researchers involved in the event are participating in the ‘Event Horizon Telescope’ (EHT), a collaborative network of astronomers, astronomers, and scientists from around the world working with nine world-wide radio telescopes to capture images of black holes.

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But how does it work and what are the current goals of the project that revealed, in 2019, the first black hole image ever recorded, Pōwehi? THE g1 spoke with Brazilian researcher and researcher Lia Medeiros, who coordinated one of the EHT studies released this week, to answer the following questions:

  1. What is the Event Horizon telescope project and what is its purpose?
  2. Where are the project telescopes?
  3. How many researchers are involved in the collaboration?
  4. How is the diagnosis made?
  5. What are the main results revealed by EHT so far?

What is the Event Horizon telescope project and what is its purpose?

The Event Horizon Telescope is the name of an international partnership that aims to get the first live images of black holes.

The main goal of the project is two large black holes: one in the middle of the Messier 87 galaxyfrom the 2019 photo, and another in the middle of our Milky Way, Arrow A *.

See the area of ​​the black hole – Photo: Art: g1

Brazilian researcher Lia Medeiros, from the US Institute of Higher Education Foundation for Studies, says that, after several others were considered, These two black holes were actually chosen because they are the largest from our point of view on Earth, which makes them easy to look at.

“So, we can achieve a better resolution for these two in particular. There are other black holes that we have also seen. But we will not be able to see the ‘small ring’ of the black hole itself in these others because it is so far away,” he explains.

What is a black hole?

What is a black hole?

Where are the project telescopes?

Je! 11 radio observationsdistributed internally 8 different locationsusually remote regions, at high altitudes and in dry air, to avoid the effects of water vapor, which makes the investigation difficult.

France, Spain, Greenland, Chile, the United States (Arizona and Hawaii), Mexico and Antarctica are the places where these tools are installed.

The location of the telescopes that make up the EHT network. – Photo: ESO / M. Kornmesser

To create the image of Sagittarius A *, astronomers used only eight observations of this network. That is because tests were performed in 2017, when the telescopes of Greenland, France and Arizona had not yet been added to the network.

Therefore, Lia explains that we can expect more detailed images of cooperation in the years to come. The researcher told it g1 who is even working on a particular project about it.

“We have a three-year investigation that we are working on. There is a lot to come. But it will not be tomorrow. [risos]”.

Southern Pole Telescope, illuminated by aurora australis and Milky Way. External site temperature reaches -60 ° C – Photo: Daniel Michalik / South Pole Telescope

How many researchers are involved in the collaboration?

There are different groups of scientists specializing in antenna enhancement, receiver enhancement, signal connection, adjustment, thinking methods, black hole theory, jet and general relationship, numerical narratives, among many other techniques.

In total, more than 300 researchers from 80 institutions worldwide working in partnership.

“A long time ago we had that idea of ​​a genius who created the theory and changed Science. We have already gone through that stage. Nowadays, a lot of research is being done collaboratively”, says Medeiros.

Lia Medeiros participated in a project that unveiled the first black hole – Photo: Reproduction / TV Globo

“This [o projeto de observação] not a result based on five people. There are many people who do different things that have contributed in different ways, from different states. People who contribute to the tool itself or who do what I do: imitations that we analyze to test the Theory of General Relationships ”

How is the diagnosis made?

Since black holes do not emit light, the main purpose of the program is to capture images of their “shadow” or “silhouette”, something that surrounds the object.

There was more than a thousand hours of radio observation. And capturing those images is not easy. Even the recently launched Hubble or James Webb cannot do this job.

“The hardest part was not making it one image, but certainly confirming that the design of the ring was real, “says Katie Bouman, a professor of Computer Science and Mathematics at Caltech and a member of the EHT network.

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He explains that scientists had to go through all the gas and dust in our galaxy to get close enough to Sagittarius A * to see this light, and that is why the network’s observations are all radio telescopes. “Visible light would be blocked by this dust, while the short radio waves we see are not affected by dust and gas near the black hole.”

“After years of complete experimentation using real and simulated data, we were finally able to conclude that there was enough evidence that the structure was ring-shaped.”

Infrastructure at Mauna Kea Observers in Hawaii, which is also part of the Horizon Event Telescope. – Photo: J. Weintroub / ESO

“But the Event Horizon Telescope telescope will be able to overcome this obstacle and have the quality of observation needed to be able to photograph the scope of events. [o ponto de não-retorno dos buracos negros]”, says Rodrigo Nemmen, a physicist and professor at the Institute of Astronomy, Geophysics and Space Science at USP, who has nothing to do with EHT work.

To illuminate the black hole, explains Nemmen, we need a photographic ability that is only possible when we truly connect telescopes scattered across the Earth into a single telescope that mimics the size of our universe. Thus, by combining the dynamics of each of these observational centers, we have an impressive resolution potential that allows for the creation of these images.

“To give you an idea, EHT will be able to photograph, in radio waves, an apple on the surface of the Moon”, says the researcher.

The process is similar to a GPS system

Brazilian Lia Medeiros, who participated in the partnership, says that GPS operation is a metaphor that helps explain how EHT works.

The GPS receiver, like the one in our mobile phones, works together with the help of satellites orbiting the Earth to determine its location. It receives waves from different satellites and calculates the time that the signal took to reach it. Since this receiver knows the location of these GPS satellites, by calculating when each signal arrives, it has the information it needs: its location.

“We use a very similar technique, because what we record is the moment that each radio wave takes to reach every one of our telescopes”, says the researcher. “We use the time that each telescope detects the calculating wave that came from the image.”

“This technique is called interferometry“, says Lia Medeiros.” We use these telescopes and they act as a team. They all point to the same place in the sky at the same time. ”

How the Horizon Telescope of the Event works – Photo: Art: g1

These radio waves are produced by a topic in plasma that creates a “circulation” of hot gas that surrounds black holes, he explains to g1 Andre Landulfo, professor of Physics at UFABC, specializes in the subject.

Thus, signals from each telescope record the radio waves that the black hole emits and combine this information with the help of atomic clocks, which ensure the accuracy of the data.

“Every telescope on Earth observes these signals, capturing the ‘image part’ of their subconscious view. Then, using modern interferometry and imaging techniques, these signals merge to form a single image (‘connecting’ different perspectives).”

But this is not immediately. On the contrary. Transporting this huge mathematical information takes time and processing.

In the 2019 photo alone, 5 petabytes of images were released (1 petabyte = 1 million gigabytes).

“It’s the equivalent of 5,000 years’ worth of files or a whole collection of 40,000 selfies of people’s lives,” compared to the project director, Sheperd Doeleman, at the time.

What important results have been revealed by EHT aside from Sagittarius A *?

The 2019 Photo was the first black hole photo record, but since then, it has not been the only photo released by the project.

Comparison of the size of two black holes: M87 * and Sagittarius A *. A white dot in the center of the image on the right shows the Sun’s diameter. – Photo: EHT Partnership (agreement: Lia Medeiros, xkcd)

In 2021, EHT astronomers uncovered a new appearance of the same black hole in the center of the 87 Messier, reflecting the sharpness of its magnetic field. (see image below).

With this picture, the researchers were able to understand a little more about one of the strangest and most powerful structures in the galaxy: the jets that a black hole can throw from its center and extend beyond its galaxy.

The first sharp image of a black hole magnet field. – Photo: EHT Collaboration

This fact is astonishing to scientists because, as we have seen, the black hole attracts everything that goes beyond its scope. However, some particles escape shortly before being caught and thrown into the air in the form of jets. And science still does not know why this is happening.

“Studies show that the magnetic fields on a black hole are strong enough to withstand hot flashes and to counteract gravity. Only gas from the magnetic field can move toward the horizon of the black hole, ”explained Jason Dexter, co-ordinator of the EHT Theoretical Working Group at the time.

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