Beyond the Sun, millions of billions of kilometers from the Earth, an invisible giant absorbs the particles of light from our Milky Voice.
Any being approaching too close would be immediately attracted, then trapped.
Nestled in the galactic center, a mysterious region around which our star revolves at more than 800,000 km/hour, this massive beast, suspected of being the metronome of our world, has just been observed for the first time.
This Thursday, the international scientific consortium Event Horizon Telescope (EHT) unveiled the very first photograph of the center of our galaxy.
Fruit of the collaboration of more than 300 scientists, this document constitutes "the first direct visual proof" of the presence of a supermassive black hole, in the heart of our island of stars.
This halo of light surrounding a dark region materializes more than half a century of scientific trial and error since the identification of the first signals emanating from the center of the Milky Way in 1974. The image confirms the theory's predictions of Albert Einstein's general relativity, a century later.
A fifty-year quest
“It is the culmination of a quest of more than 50 years to determine what is at the center of the galaxy.
Being able to photograph this black hole is a source of great pride”, says Vincent Piétu, astronomer at IRAM, member of the EHT and co-signatory of the study retracing this discovery, published this Thursday in The Astrophysical Journal Letters.
To make the invisible visible, the EHT simultaneously mobilized eight astronomical observatories scattered around the world.
One of the many telescopes used, that of the Institut de radioastronomie millimètre (IRAM), an organization financed by CNRS (France), the Max-Planck-Gesellschaft (Germany) and the Instituto Geografico Nacional (Spain) provided, "the sharpest images, thus contributing decisively”, thanks to its 30-meter long antenna, underlines the CNRS.
In April 2017, for about ten nights, scientists recorded the light emanating from the incandescent electrons which revolve around Sagittarius A*, a mass equivalent to four million times the Sun then suspected of being a black hole.
“The orbit of the stars around the center of the Milky Way indicated the presence of a massive object in a very small region.
In theory, only black holes have these characteristics, but we needed proof,” says Vincent Piétu.
Then for five years, the researchers struggled to develop a clear image of the halo.
This disc of matter rotates quickly and to detect it, it takes a long exposure time.
“We take a photo of a puppy biting its tail and doing 5 turns on itself while the shutter button is pressed”, vulgarizes the specialist in protoplanetary discs.
A major step forward
A century after Albert Einstein's work was published, his equations worked: "We were amazed at how well the size of the ring matched the predictions of Einstein's theory of general relativity," said EHT project scientist Geoffrey Bower of the Institute of Astronomy and Astrophysics at Academia Sinica in Taipei, in a statement.
Why can't you take a picture of a black hole?
With this shot, scientists will compare our black hole with that of the galaxy M87, the first black hole photo ever recorded, taken by the EHT in 2019. And try to find out why they seem to be lodged in the heart of each galaxy: " These unprecedented observations have significantly improved our understanding (…) and offer new insights into how these giant black holes interact with their environment,” the researcher also said.
A major step forward, which would not have been possible without international cooperation, at a time when war is returning to the European continent: "This discovery is the result of pooling technological instruments and various skills .
It brings together researchers from all over the world.
We wouldn't have had this result alone,” underlines Vincent Piétu.
Next step ?
Go beyond the simple image, and film a black hole, for the first time.