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Comment: what it means to "see" really a black hole

"We have seen what we thought was not visible," said the astronomer, as if someone who knew that the ear of the story is pressed against the door. He remained in the silent attention of the room in Washington when he called the image on the screen behind him. You already know: a ring of smoke, an orange donut, a blurry circle of light closed around in deep darkness. At the end of the day, it would be familiar to millions of people as the first picture taken of a black hole.

The Event Horizon Telescope (EHT), a collaboration of eight radio telescopes from around the world, gathered this image from observations made from Antarctica and Arizona. Because no telescope is powerful enough to distinguish a detail as small as a black hole 55 million light-years away, scientists took advantage of these eight observatories to simulate a much larger instrument, one as large as Earth. It took two years and more than 200 people sifted and refined the data collected in four days in April 2017 to focus on the famous final image.

Seeing the echo of the story in the news on Wednesday, I was surprised by the profound simplicity of this image, obtained through such complex means. Disconcerted through algorithms and vectors, the photo is not a representation of an artist or a model, our previous stabs in the image of a black hole, but it is still a construction. The radio waves collected by the telescopes and assembled in the image are translated into color for our benefit. You can not raise a telescope, not even the size of the Earth, and see it for yourself. And yet, throughout the day, I heard a line repeated over and over again: we are seeing a black hole. He did not "detect" it by his radio firm, he did not discover any more evidence of its existence, actually seeing it.

Much larger than its scientific value, in addition to its pure technological achievement, the experiment is perhaps the most notable for not nullifying the established rules of relativity; the image seems important to us because it is an image. Our certainty, translated into undeniable orange and black, has a new weight.

We did not lack proof that black holes existed. Since Albert Einstein reluctantly predicted them with his theory of relativity in 1916, we have been gathering evidence. In 1935, physicist Subrahmanyan Chandrasekhar hypothesized that a star could become so massive that it would collapse under its own gravity. Then, in 1969, Donald Lynden-Bell suggested that supermassive black holes at the center of galaxies could be responsible for the huge energy signatures detected there, far beyond what the stars could generate. In 2015, the almost definitive test came with the cosmic "zing". that was the sound of two black holes colliding, a billion light-years away. For most scientists, the detection of gravity waves encased it: there were black holes out there, stirring space-time, even if we never saw them.

However, the images of outer space have a strange power over us: these are views so supernatural that they never conform to our understanding. Naked, our eyes perceive the night sky as a cosmic swirl of dust and diamonds, indications of greater complexity. In the early 1600s, Galileo and others aimed the first telescopes at the sky to describe the mountainous face of the moon, the dark spotted sun spinning slowly on its axis, the three glittering moons of Jupiter reeling in their distant orbits. The sight gave us irrefutable proofs of the immensity of the universe, its chaotic and chaotic physics. And, seeing all this for the first time, we believed in it.

I grew up under these cosmic visions. I remember sleeping under posters of the Pillars of Creation and the Eye of Cats Galaxy at the Space Telescope Science Institute in Baltimore, while my mother reviewed the data and grant proposals on her desk. When I was a little older, I amused myself by throwing a toy propeller in the corridor, to see how it moved along the currents that moved above my head. My mom told me that looking in space with a telescope was like looking back in time. Nothing disappeared from the universe, he said, he simply walked away. I understood that this means that everything could be known, if we could see enough.

Our telescopes are bigger and more powerful than ever. They are mirrors that lean towards the sky from the tops of mountains and deserts, or that float in orbit like huge insects in their rigid wings of solar cells. They swallow light, not only the visible spectrum of blues and reds, but also the X-rays and radio waves to which we are blind, revealing the intricate structures of distant galaxies and misty Technicolor nebulae. These are landscapes that we could never see for ourselves, but when we see their images, they become real to us.

Even so, black holes had eluded us. They are the definition of what can not be seen: mass and volume turning inside outwards, cosmic sinks whose irresistible gravity of which nothing can escape, not a single bad photon.

But light has always helped us understand what we could not see: T.S. Eliot wrote about the "visible reminder of invisible light," tracking what is seen and what is not seen. The first astronomers inferred the invisible presence of gravity by the arcs of stars around their pivots. The moderns use the oscillating brightness of the stars to guess the planets that can orbit them, which causes these distant suns to lose their balance. And Hubble's observations of an expanding universe, reflected in the distorted light, have revealed the presence of dark matter, an idea so strange and slippery that it is difficult to acquire it.

At the Science Institute of the Space Telescope, my mother was also studying black holes, which the scientists were beginning to understand were sitting in the center of most galaxies, spinning their skirts of stars around them like dervishes. We could not see them, but we could see the radiant clouds of light and energy that surrounded them. The paradox of the black hole is that, while no light can escape its limits, the regions beyond the event horizon are some of the most energetic and bright places in the universe. From it, I saw how you could follow the trail of the visible, looking for signs of the invisible.

Behind the image of the halo in the center of Messier 87, one of the two galaxies in the crosshairs of the EHT, is a reminder of the challenges we face when looking for these objects that can not be seen. The second objective of the EHT, Sagittarius A *, is the black hole at the center of our own galaxy. Although much closer to us than M87, it is also smaller and, therefore, more prone to change focus, like a restless student on the day of photography.

But, invisible, it is made known. In the center of bright light of the Milky Way, the stars throw shots in tight orbits around a massive, invisible object, accelerating with each brush that passes through the engine turning there, and then slowing down at the zenith before returning to turn. We can see them clearly. We can discern, by their dance, what has them in captivity. We can not see it yet. But we know it is there.

Amelia Urry is a science writer and poet in Seattle. She is also the daughter of two astrophysicists.

Amelia urry
Amelia urry

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