More than 1,500 scientists, as well as research institutions and companies from 25 countries, are working together to build the Cherenkov Telescope Array (CTA), which will have more than 100 networked telescopes and will be the largest observatory for extreme energy sources, like the gamma rays of the world.
And all under the leadership of a Brazilian scientist, astrophysicist Luiz Vitor de Souza Filho, from the Physics Institute of the University of São Paulo, in São Carlos (IFSC-USP).
Its implementation began in 2013 and, after several delays, its completion is scheduled for 2025. When fully operational, there will be 118 telescopes of various sizes, some of them 23 meters in diameter. Of this total, 99 will be installed in the Chilean Andes, in the Cerro Paranal region, and 19 on the Canary Island of La Palma, Spain.
CTA owes its name to the Cherenkov effect, discovered by Russian physicist Pavel Alexeevitch Cherenkov. Along with his compatriots Igor Yevgenyevich and Tamm Il’ja Mikhailovich Frank, he was awarded the Nobel Prize in Physics in 1958.
“The Cherenkov effect is the emission of radiation (light) resulting from the passage of a charged particle with a velocity greater than the speed of light in a medium, such as water or air, for example”, explains Souza. “That is, when an electrically charged particle crosses the Earth’s atmosphere, it produces a light trail, which can be detected by CTA telescopes.” The speed of light cannot be exceeded only in a vacuum.
Some numbers help to understand this better. The speed of light in vacuum (c) is 299,792.458 km/s and is unsurpassed. But in any medium it is less than this value. In air near the Earth’s surface, for example, the speed of light is approximately 299,702 km/s.
The speed of an electron in air can be greater than this value, but it must be less than 299,792 km/s, that is, it is greater than the speed of light in that medium, but less than it in a vacuum. In short, nothing, whether in a vacuum or in any other medium, can surpass the speed of 299,792 km/s.
In search of extreme events
The CTA telescopes will look for gamma rays – also known as cosmic rays – which are emitted by the most extreme events known in the universe, such as supernova star explosions and black hole collisions.
“The CTA will be the next generation of telescopes dedicated to gamma radiation astronomy, therefore, for observing the sky in the most energetic range of the electromagnetic spectrum”, explains astrophysicist Ulisses Barres de Almeida, from the Brazilian Center for Physical Research (CBPF) and one of the three main researchers of CTA in Brazil – together with Souza and physicist Elisabete Dal Pino, from the Institute of Astronomy, Geophysics and Atmospheric Sciences (IAG) at USP
“The observatory will investigate the most energetic events in the universe, including the physical conditions of cosmic particle accelerators, such as black holes, pulsars, supernovae and gamma radiation bursts; in addition to the composition and origin of dark matter, the magnetic fields of the universe, and the violation of the constancy of the speed of light, which is only possible to measure in gamma rays”, explains Dal Pino.
According to her, the new observatory will have an improvement in sensitivity of a factor 5 to 10 times more than the current ones at energies between 100 gigaelectron volts (GeV) and 10 teraelectron volts (TeV). By definition, an electron volt is the amount of kinetic energy gained by a single electron when accelerated by an electrical potential difference of one volt, in a vacuum.
“With the CTA, it will be possible to detect gamma rays from the cosmos in a range that ranges from energies well below 100 GeV to above 100 TeV, reaching energies never before observed in the universe”, says Elisabete.
To cover this extensive energy range, the observatory will have three different sizes of telescopes: large (LST), with 23 meters in diameter, medium (MST) with 15 meters, and small (SST) with 4 meters in diameter.
Through the observation that will be made by the set of telescopes, it will be possible to reconstruct the direction and energy of the gamma radiation that is coming from distant sources in the universe.
“The CTA is a broad and multiple experiment designed to make discoveries rather than incremental measures,” explains Souza. “The results of the new observatory will provide information on macro (astro) and micro (particles) scales of nature.”
According to astronomer Reinaldo Santos de Lima, from IAG-USP, who is also participating in the project, more information, details and statistics from astrophysical sources, such as supernovae, pulsars, active nuclei of galaxies, or even extensive regions of the galaxy where radiation from energy, make it possible to understand more about the physical conditions of these sources and environments.
“They also help to understand the processes of generation and fundamental interactions of the super-relativistic particles that generate this radiation, the cosmic rays”, he adds.
The CTA will also help to understand how fundamental particles (protons, neutrons, electrons, for example) interact on energy scales inaccessible in experiments on Earth, such as the Large Hadron Collider (LHC) particle accelerator or Large Electron-Positron Collider, installed in Switzerland.
“Such energetic scales of particle interaction were common in the first moments of the universe after the Big Bang, but they can only be studied today in these extreme astrophysical phenomena”, explains physicist and astronomer Aion da Escóssia Melo Viana, a colleague of Souza at IFSC-USP. , and also a member of the observatory.
Furthermore, says Viana, there is the possibility that the nature of the mysterious dark matter may finally be discovered, through its annihilation or disintegration in the centers of galaxies (such as the Milky Way itself), which would produce a faint light in gamma rays. that can be detected by the CTA.
Brazil at the forefront of the project
It is not by chance that Brazilian researchers are participating, with prominent positions, in the most advanced observatory to be built.
“Brazil has a long experience in this area of research that is called Particle Astrophysics (formerly the most used name was cosmic rays)”, explains Souza.
According to him, among the first scientific articles on physics published in international journals were results in this area of research, with the Brazilian authors Marcello Damy and Paulus Pompéia, in 1940.
The best-known Brazilian physicist, César Lattes, also made his career in this area of research. “These pioneers planted the seeds of a community that today participates in the CTA”, proud Souza.
Also according to him, in the last two decades, the Brazilian community has opened new perspectives for national participation by involving the industry in the construction of large observatories, such as the Pierre Auger, in Argentina, and the Southern Astrophysical Research Telescope, better known as SOAR, in Chile. .
Brazil also participates in the experiments of the European Organization for Nuclear Research (CERN), which operates the LHC, whose instrumentation has some similarities with Particle Astrophysics observatories.
Souza says that these initiatives in recent decades have placed the national Particle Astrophysics community at the highest level of science being done in this area.
Thus, the country has become an important partner by contributing scientific knowledge and technological innovation.
“That’s why in 2010 I proposed to the International Consortium of CTA the inclusion of Brazil”, he says. “Due to the history, we were accepted. Then, I started the task of forming a national team and prospecting companies interested in participating. It was an arduous path, but after 11 years, we achieved scientific prominence in the Consortium and participation of the national industry in the construction of the telescopes.”
He himself was recently elected, for a two-year term, as president of the scientific assembly of the CTA, the observatory’s highest body for the area of science and research.
“My choice is the result of a long history of success in the field of Particle Astrophysics in Brazil and, in particular, of the participants in the CTA”, he says. “Today we are already more than 50 people involved with CTA in Brazil. I feel very honored and challenged to take on this responsibility. The Observatory is in a very important stage of transition between prototypes and the definitive construction of the telescopes in the places where they will be installed, which will require a lot from the presidency of the assembly.”
In addition to the researchers, Brazilian companies are also participating in the construction of the observatory. This is the case of Orbital Engenharia, from São José dos Campos (SP), which won a competition with a company in Europe to develop the project and build the mechanical support structure (arm) for the cameras of medium-sized telescopes.
“It is approximately 16 meters high and will be installed in telescopes with a 12-meter-diameter mirror, to support and position the two-ton camera”, says the company’s president, Célio Costa Vaz.
This structure has various requirements for design, fabrication, interfaces, transportation, assembly, and operating life in harsh environments, including earthquake resistance.
Souza says that, for Orbital Engenharia, “with its vocation and vast experience in the development of its own technologies aimed at space applications in the country”, this choice proved to be an opportunity to apply its space engineering capacity in a challenging project of international relevance. . “It also made it possible to open up a new market, that is, to provide engineering support to scientific research in astrophysics at a global level,” he says.
Source: CNN Brasil
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