July 2, 2022

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It wasn't just a feat.  This is the purpose of "capturing" a black hole.

It wasn’t just a feat. This is the purpose of “capturing” a black hole.

Sagittarius A* is located 27,000 light years from Earth. / EHT Collaboration

Photo: EHT Collaboration

On May 12, at the simultaneous press conferences of the Event Horizon Telescope (EHT) collaboration, we “saw for the first time the silhouette of the supermassive black hole living at the center of our galaxy: Sagittarius A*. This compact object is named after the constellation Sagittarius where it is located. Bracket A* (or Sgr A*) is A Black hole With a mass 4 million times the mass of our Sun, it is a true giant. It took 27,000 years for the light from the superheated material surrounding this object to reach our telescopes. In the image, the silhouette has an equivalent extension to the orbit that Mercury sweeps around the Sun. (Read Women in Science in Colombia: the gap is also noted in publications)

to Realizing the “vision” of this objectby definition of darkness, it was required to create a set of 8 radio telescopes At different points on the planet, which leads to obtaining an image with a resolution similar to observing a donut on the moon’s surface with the naked eye from Earth. This great engineering feat would have been impossible without the joint work of the more than 300 scientists involved in the project around the world. (Read the amazing pictures left behind by the lunar eclipse in the world)

But, What are we really seeing In this picture so prevalent these days?

The silhouette of this “gentle giant,” as it was named at a press conference, due to its low activity and low rate of matter accumulation, is a reconstruction of hundreds of superimposed images of radiation whose path is bent by the massive gravitational field around it. from the black hole. The bright ring shows the radiation that heats the gas in the environment of the pressurized body. This donut-shaped substance is very close, but it has not penetrated the event horizon or the point of no return, an area from which not even light can escape. In the center, the dark region contains the event horizon covering the singularity.

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To capture this “photo” of the Sgr A* shadow, an array of powerful radio antennas located from Hawaii to Spain, from the United States to Antarctica were used. However, a significant difference has been made by the Atacama Large Millimeter/submillimeter (ALMA) array in Chile – due to the high sensitivity achieved by the 66 antenna array found in the Atacama Desert. Separately, none of these telescopes will be able to resolve this object, but these instruments together make up a telescope close to the size of Earth.

The technique used by the EHT collaboration is known as VLBI (Very Long Basic Interferometry), and it has already revealed the image of the supermassive black hole from galaxy Messier 87 (M87) in April 2019.

By comparing Sagittarius A*, located in the center of the Milky Way, with the black hole of M87, we find that the latter is 1,500 times larger. The center of M87 is located 55 million light-years from Earth, and exhibits powerful jets and a massive amount of mass accretion. However, the silhouettes of both black holes look very similar in size and angular shape.

But It’s the first time we “see” Arch A*.. In 1933, Karl Jansky reported a radio signal coming from the galactic center, in the constellation Sagittarius, which was confirmed in various later observations. In the 1990s, Reinhard Genzel studied this highly compact object using infrared spectroscopy and longer wavelengths, and recently, two independent research groups have been tracking the orbits of stars near the supermassive black hole for years. From the observations, the estimated mass of the body responsible for these orbits is found. This study led to Andrea Ghez (UCLA) and Reinhard Genzel (LMU) being awarded the Nobel Prize in Physics in 2020.

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The concept of a black hole is not new. Since the eighteenth century, John Michell, the English natural philosopher, has used the idea of ​​escape velocity to postulate the existence of black Stars, objects whose density is so high that light cannot escape the influence of gravity. At about the same time, Immanuel Kant postulated that very massive objects should be found in the centers of galaxies, anticipating the modern idea of ​​supermassive black holes in the cores of larger galaxies. Even Edgar Allan Poe, the American writer, made interesting predictions of cosmology that were overlooked in his day, including very massive objects that have powerful influences around them.

The modern description From these gravitational giants arises from General theory of relativityone of the great contributions of Albert Einstein. The first solution to field equations is due to Karl Schwarzschild, and it was published in 1916 while serving in the German Army in World War I. His equations describe a black hole caused by the gravitational collapse of a star. Later solutions include black holes that, in addition to mass, exhibit rotation and electric charge.

The Einstein’s gravitational theory It also predicts the deflection of light due to the presence of mass in spacetime, the dimensions of the event horizon or the generation of gravitational waves through the merging of very massive objects.

At this point, it is important to note that a black hole at the center of our galaxy will not occur devour to the solar system or the stars close to it, in the same way that the planets in the solar system maintain stable orbits around the sun, without the latter dragging it to its center. It is a delicate balance between gravity and the relative distances between objects of mass.

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It should also be clarified that the achievement of arc capture A* represents the overcoming of technical difficulties such as taking measurements while immersed in the same galaxy, Watch Dust-blocked body and Milky way gas and correction for the signals obtained by the rapid variation of the orbitals around Sgr A*.

The silhouette of Sagittarius A* not only confirms that this object is indeed a black hole, and thus demonstrates the correctness of Einstein’s relativity, but also leaves behind important technological and conceptual developments. Sophisticated AI algorithms used by EHT scientists to process signals from telescopes up to 4 gigabits per second can now be applied in fields as diverse as meteorology, banking, cybersecurity, communications, and emotion analysis, marketing or social networks.

On a more fundamental level, the It will allow us to study black holes Understand the mechanisms of formation of supermassive black holes, the influence of these objects on the evolution of host galaxies, and the complex interaction of gas, dust and radiation in the vicinity of black holes. In addition, black holes could be a gateway to long-awaited quantum gravity, because in a singularity the laws of physics as we know them would be broken.

Physicists’ dream of building a grand unification theory might be a little closer if we understand what happens to spacetime when a black hole forms. What is certain, for now, is that we are witnessing a historic moment since we began studying our galaxy: We are looking straight into the heart of that big patch of milk in the night sky where our solar system is.

* Ph.D. in Astronomy – Research Professor ECCI University

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