‘Black Hole Hunter’: What is the Event Horizon Telescope and what are its search milestones?  |  science

‘Black Hole Hunter’: What is the Event Horizon Telescope and what are its search milestones? | science

Scientists from an international consortium released a photo for the first time on Thursday (12). Of A *A huge black hole in the center of our Milky Way galaxy.

Researchers involved in the event are taking part in the Event Horizon Telescope (EHT), a collaborative network of astronomers, astrophysicists and scientists from around the world who are working around the world to capture images of black holes. Spread nine radios work with binoculars.

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But how does it work and what are the current goals of the project that revealed, in 2019, the first image of a black hole was recorded, Pōwehi? The g1 He spoke with experts and with Brazilian researcher Lea Madiros, 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 binoculars?
  3. How many researchers participate in the collaboration?
  4. How are observations made?
  5. What are the key findings from EHT so far?

What is the Event Horizon Telescope Project and what is its purpose?

Event Horizon Telescope is the name of an international collaboration aimed at obtaining the first live images of black holes.

The project focuses on two supermassive black holes: A Messier 87 in the center of the galaxyFrom the picture of 2019, And another in the center of our Milky Way galaxy, Sagittarius A *.

View the location of the black hole – Photo: Art: G1

After several other observations, Brazilian researcher Lea Madiros, from the Institute for Advanced Studies at the National Science Foundation of the United States, says: These two black holes were specifically chosen because they are the largest on Earth from our point of view, which makes them easier to observe.

“Therefore, we can reach the best resolution, especially for both of them. There are other black holes that we have observed. But we do not see the ‘little ring’ of black holes for these others.” Because they are far away, “he says.

What is a black hole?

What is a black hole?

Where are the project binoculars?

Are 11 Radio ObservatoryDistributed in 8 different locationsUsually in remote areas, at high altitudes and with dry environments, to avoid the effect of water vapor, which makes observations difficult.

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

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

To image Sagittarius A *, astronomers used only eight observatories in the network. That’s because the measurements were made in 2017, when Greenland, France and Arizona telescopes had not yet been added to the network.

Therefore, Lia explained that we can expect more detailed pictures of cooperation in the coming years. The researcher said g1 Who is also working on a specific project about it.

“We have three years of observations that we are working on. A lot is to come. But it will not happen tomorrow. [risos]”

Bright with South Pole Telescope, Aurora Australis and Milky Way. Outdoor temperature at the site reaches -60 ° C. – Photo: Daniel McCallick / South Pole Telescope

How many researchers participate in the collaboration?

There are various groups of scientists specializing in antenna optimization, receiver development, signal correlation, calibration, imaging methods, black hole theory, jet and general relativity, numerical simulation, and many other techniques.

In total, more than 300 individual researchers from 80 institutions Work collaboratively around the world.

“A long time ago we had the idea of ​​an intelligent person who made a theory and changed science. We have already gone through this stage. Nowadays, most of the research is done collaboratively,” said Maderos. Added

Lia Madeiros took part in the project that unveiled the first image of a black hole – Photo: Reproduction / TV Globo

“It [o projeto de observação] This is not a result that depends on five people. There are a lot of people who do very different things who have collaborated with different states in different ways. People who contribute to the tool themselves or do what I do: the simulations that we analyze to test the theory of relativity. ”

How are observations made?

Because black holes do not emit light, the program’s primary mission is to capture images of its “shadow” or “satellite,” which revolves around the object.

There was more than a thousand hours of radio observation. And getting these images is not easy. Even Hubble or the newly introduced and ultra-modern James Webb can’t do it.

“It simply came to our notice then. One Photo, but in fact confirming that the ring was real, “says Katie Bowman, a professor of computer science and math at Caltech and a member of the EHT network.

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She explains that scientists had to go through all the gases and dust in our galaxy to get close enough to see this circle of light to Sagittarius A *, and that is why network observatories are all radio telescopes. “The visible light will be blocked by this dust, while the short radio waves we observe are not affected by dust and gas near the black hole.”

“After years of literal testing, using real and simulated data, we finally came to the conclusion that there is overwhelming evidence that the structure is ring-shaped.”

Infrastructure at the Mona Kia Observatories in Hawaii, which is also part of the Event Horizon Telescope. – Photo: J. Weintroub / ESO

“But the Horizon Telescope manages to overcome this obstacle and has the quality of observation to be able to capture the horizon of the event. [o ponto de não-retorno dos buracos negros]”This is not about the work of EHT,” says Rodrigo Neiman, a professor and professor at the Institute of Astronomy, Geophysics and Atmospheric Sciences in the USP.

In order to focus on black holes, Neyman explains, we need imaging power, which is possible only if we combine telescopes scattered all over the earth into practically a single telescope that can capture our world. Duplicate the size. Thus, combining the power of each of these observatories, we have an impressive resolution capability that allows these images to be created.

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

This process is similar to the GPS system.

Brazilian Lia Madeiras, a participant in the collaboration, said the GPS operation was an analogy that helped explain how EHT works.

A GPS receiver, as in our cell phone, works closely with satellites orbiting the earth to pinpoint its exact location. It receives signals from various satellites and calculates how long it takes to reach that signal. Because the receiver knows where these GPS satellites are, by calculating the arrival time of each signal, it has the information it needs: where it is located.

“We use a very similar technique, because what we are recording is actually the time it takes for each radio wave to reach each of our binoculars,” said the researcher. “We use the time each telescope detects the wave to calculate where it came from in the image.”

This technique is called. Interfumery“Leah Mediros,” she says. We use these binoculars and they work as a team. They all point to the same place in the sky. ”

How the Event Horizon Telescope Works – Photo: Art: G1

These radio waves are emitted by the substance in the plasma, which creates a “swirl” of hyperheated gas around some black holes. g1 Andre Landolfo, Professor of Physics at UFABC, specializes in this subject.

In this way, the signal coming from each telescope records the radio waves that emit a black hole and combines this information with the help of atomic clocks which guarantees the accuracy of the data.

“Every telescopic station on Earth observes these signals, takes a ‘partial picture’ of their limited perspective. Then, using the latest interfumetry and imaging techniques, these signals are combined to form an image. (‘Uniting’ different perspectives) “.

But it is not immediate. On the contrary. Transferring this huge amount of computational information takes time and further action.

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

“That’s the equivalent of 5,000 years worth of mp3 files, or a whole bunch of selfies of 40,000 people’s lifetimes,” compared Shepard Doyleman, then project director.

What are the key findings from EHT other than Sagittarius A *?

The 2019 image was the first black hole photographic record, but since then, it is not the only image released by the project.

Comparison of the size of two black holes: M87 * and Sagittarius A *. The white dot in the center of the image highlighted on the right represents the diameter of the sun. – Photo: EHT Collaboration (Confession: Lia Maderos, XK CD)

In 2021, EHT astronomers unveiled a new view of the same black hole at the center of Messier 87, showing a sharp image of its magnetic field. (See picture below).

With this image, researchers were able to understand a little more about one of the galaxy’s most mysterious and energetic structures: the jet planes that the black hole manages to launch from its center and which from its galaxy. Spread out

The first sharp image of a black hole’s magnetic field. – Photo: EHT collaboration

This phenomenon amazes scientists because, as we have seen before, a black hole attracts everything that passes through its event horizon. However, some particles escape just moments before being captured and are sent into space in the form of jets. And science does not yet know why this happens.

“Observations show that the magnetic field at the edge of the black hole is strong enough to resist the pushing of hot gas and the pulling of gravity. Jason Dexter, then coordinator of the EHT Ideological Working Group, explained.

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