The very first image of the Milky Way’s black hole has just been published

The ESO (European Southern Observatory) had given an appointment to all the curious people of the whole Earth. Three years ago, the observatory had already upset our version of the Universe, by publishing the very first image of a black hole. At the time, it was M87, a black hole located more than 53 million light-years away.

Far from being the closest black hole to Earth nor the largest in the Universe, the galaxy M87, and the black hole at its center was the ideal candidate according to the ESO and the EHT (Event Horizon Telescope) . Thanks to its distance from Earth, it was easy to sort out the stars and the black hole. A much more complicated thing to do for a black hole close to us, like Sagittarius A*, which sits at the center of our Milky Way.

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An improved version of the first image of a black hole, that of the galaxy M87 © Event Horizon Telescope

Historic work by the EHT

To better realize the magnitude of the task when capturing the image of M87, the computer data collected by the radio telescopes was so numerous that it was easier for the various observatories to copy this data and transfer it manually, from a physical hard disk (which therefore went to California where all the data was centralized). The plane trip was indeed shorter than the transfer of data by optical fiber.

If everyone had been surprised by the result obtained three years ago, he who came to validate Einstein’s theory of general relativity, many people expected in the hours which preceded the announcement that he s This is a photo of Sagittarius A*, the black hole at the center of the Milky Way, our galaxy.

A first image of Sagittarius A*

At the time, the ESO and EHT teams had explained that there was too much “noise” to have a clear image of the black hole, in particular because of the many planetary systems which bar the passage of radio telescopes in permanently, greatly disturbing the observations.

But now, three years later, the image of Sagittarius A* has just been published by the EHT. A real tour de force for observatories around the world. To get an idea of ​​the accuracy of this image, the ESO explains that it is possible to see the details of a New York building from the top of the Eiffel Tower with such image quality.

Another crazy idea, to realize the importance of the work accomplished, all the data collected in this experiment, printed on A4 sheets would be able to go from the Earth to the Moon.

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A comparison of the two images we have at the moment (M87 on the left, Sagittarius A* on the right)© EHT

What is a black hole?

A black hole occurs when a massive star collapses. This is also the ultimate stage of the collapse of matter. Gravity becomes so important at a specific point in the Universe (the singularity) that light can no longer leave the black hole, which is not going fast enough (300,000 km/s) to detach itself from gravitational forces.

It is therefore true to say that “nothing can come out of a black hole, not even light”. Often described as vacuum cleaners for matter, black holes cause matter to “drop” into their center. In general they are located in the center of the galaxies. By their mass and their gravitational force, they manage to maintain a certain balance in the Universe.

Theorized by Albert Einstein at the beginning of the 20th century in his theory of general relativity, black holes were therefore only proven in 2019, when the image of M87 was published. Although we knew that the Earth revolves around a black hole, like the rest of the galaxy, we had never had images of it, so that’s what is done.

It will be interesting to see in the coming months how this image can evolve and how the EHT intends to improve it further, they who have already announced that they have enough material to update the photograph of Sagittarius A *.

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