The bingo radio telescope under construction in Paraíba will seek a signal of the first sounds of the universe – Sidereal Messenger

We know that musical success is a matter of time. A large radio telescope under construction inside Paraíba should now specifically investigate what fashion sounded like in the beginnings of the universe shortly after the Big Bang, thus clearing up two of the greatest mysteries of modern times, science: what they are, dark energy and dark matter. The so-called bingo project was officially presented this Tuesday (6) off-site via the Internet.

The international initiative, led by Brazil, has participants from China, Great Britain, France, South Africa and Germany. “We lost a lot of time due to the pandemic, but the instruments are under construction and we hope to be able to enter the commissioning phase of the radio telescope by the end of 2022,” said Elcio Abdalla, project coordinator and researcher at the USP Physics Institute (University of Sao Paulo. ). ).

The initiative has an estimated cost of between R $ 15 million and R $ 20 million, with funding from FAPESP (São Paulo State Research Support Foundation), MCTI (Ministry of Science, Technology and Innovation), Finep (studies financier). and projects) and the government of Paraíba. The Brazilian research institutions most heavily involved include USP, UFCG (Federal University of Campina Grande) and Inpe (National Institute for Space Research).

And of course, bingo follows the tradition of astrophysicists with cute acronyms: It is a summary of Baryon Acoustic Oscillations from Integrated Neutral Gas Observations or Baryon Acoustic Oscillations in Integrated Neutral Gas Observations. In short, the record of the signs left by the ancient sounds that streamed through the cosmos more than 13 billion years ago when it was just a dense plasma.

THE BALLAD OF THE UNIVERSE
Calm down, don’t despair because you don’t quite understand what this conversation is about. Let’s break this down, starting with Big Bang. Usually represented as a large explosion, it is actually best thought of as a large dilution from expansion. Imagine that at the beginning of it all, 13.8 billion years ago, all of the matter and energy in the universe was concentrated in a single point. This point was then inflated like a balloon and the cosmic contents expanded and thinned. It cooled down in the process. Particles formed. But still very hot, they were moving at a very high speed. The light, in turn, could not advance without hitting a particle. Electrons could not be captured by protons and neutrons and formed neutral atomic nuclei. This disorganized mass is called plasma. The sun, for example, is made up of plasma – its atomic nuclei and electrons are too hot to exist in a stable combined form.

With the well-known laws of physics, scientists can reasonably describe what happened in this primordial plasma. First, it wasn’t completely homogeneous (quantum physics forbade it), which means it was like a lump full of lumps. Second, the light particles were trying to come out the whole time (I imagine they were screaming, “Let me through, let me through!”) As they hit surrounding particles of matter.

Inhomogeneous meant that there were places with a higher density of baryons (protons and neutrons) than others. Where the density was greater, gravity exerted more inward force, namely compression. But the photons (particles of light) continued to strive to free themselves, an external force. The combination of the two generated acoustic vibrations. That’s right, sound waves passed through this primordial dense plasma. Acoustic vibrations of baryons.

The expansion continued, the dilution increased, until finally light could penetrate without collision, while atoms could form that stably combined protons and neutrons with electrons (what cosmologists confusingly call the “recombination epoch”, since these particles have never met before combined). This happened about 380,000 years after the Big Bang, when, it is poetically said, the universe became transparent.

The first photons that cry out for freedom keep wandering after traveling more than 13 billion years, and the number is growing. We recognize them in the form of microwaves. Since this radiation comes from all sides, the result of the expansion of the cosmos after the Big Bang, we call it cosmic microwave background radiation.

Image of the cosmic microwave background radiation, recorded by the Planck satellite. (Image: ESA)

And such acoustic vibrations that also circle? No. Remember: sounds need matter to spread. The price for making the universe transparent was also the price for being mute. But at that time these waves caused changes in the distribution of matter in this primordial plasma, which would later be reflected in the organization of the cosmos in galaxies, large star clusters and gas. By looking at the distribution of matter in our larger cosmic environment, we can look for the pattern of acoustic vibrations that occurred in the “opaque” phase shortly after the universe was formed.

It’s not an easy task: imagine throwing hundreds of stones into a lake and, after each of the circular waves created overlap with the others in a complex pattern, take a picture and try to identify each of them individually . Now go ahead and imagine that this happened in the universe in three dimensions – the circles in the lake turned into bubbles that occurred at different depths.

Despite the difficulty, we already have some well-documented evidence of this pattern. The measurements of the cosmic background radiation allow us to estimate how big the density bubbles generated by the acoustic oscillations were when the universe became “silent”, the so-called “sound horizon”. And on the other hand, large sky scans, such as the famous Sloan Digital Sky Survey (SDSS), made it possible to find these patterns in the distribution of galaxies, suggesting that the ancient sonic horizon in today’s universe is about 500 in size after billions of years of expansion Millions of light years. This is the main action that Bingo intends to take, but with a view to distributing neutral hydrogen.

THE RIGHT PLACE
The researchers around Elcio Abdalla searched all of South America, especially Brazil and Uruguay, where they were able to accommodate the large radio telescope. They finally decided on Serra da Catarina in the rural area of ​​Aguiar in the interior of Paraíba. The selection criteria were the local geography and isolation, which make the region the least likely of all visitors to radio interference caused by human activities.

The design of the radio telescope is unique to the project, with a main reflector 40 meters in diameter and a secondary reflector 36 meters and a tower with 28 horns to receive the signal reflected from space. The system is solid, which means that the instrument is not “pointed” (like the famous Arecibo radio telescope that was recently deactivated in Puerto Rico). Instead, it records observations of what is up in the sky, and the Earth’s rotation itself will “show” so that bingo can record about an eighth of the celestial sphere in its observations.

The main goal is to measure radio waves 21 centimeters long, associated with the presence of neutral hydrogen (an electron that rotates around the nucleus and offsets the positive charge of its single proton). The data will enable us to observe its distribution at a distance of several billion light years. Bingo is said to be the first instrument that recognizes the patterns of acoustic vibrations of baryons by radio.

Precise measurements, in turn, can provide good clues about dark matter and dark energy, two entities that we only know from indirect effects, but whose nature is not yet understood. And what hurts the most: They make up 95% of all matter and energy in the universe. The so-called baryonic matter, which forms all directly detectable objects, from the atom to the star, makes up only 5%.

We know that dark matter exists because it creates gravity even though it does not interact with light. And of course its gravitational contribution is part of the recipe for the acoustic vibrations that occur back there in the primeval plasma after the Big Bang. The precise measurement of vibrations helps to delimit their effects and to compare them with explanatory hypotheses.

Dark energy, on the other hand, is a mysterious force that has accelerated cosmic expansion for about 5 billion years. Nobody knows what it is, but since it affects expansion, it also affects the size of the bubbles left by acoustic vibrations.

By doing this, it is hoped that bingo will help clear up these great mysteries. But not just this. The researchers also bet that the radio telescope will be useful for studying so-called rapid radio bursts, a phenomenon that has been discovered over the past decade and involves very rapid and intense bursts of energy. They’re still largely mysterious and come in many flavors; some appear to be periodic or non-repeating, others are unique events. We are talking about high energy cosmic events that may be associated, at least in some cases, with neutron stars with very strong magnetic fields, but their exact nature is not yet clear.

When Albert Einstein confirmed his general theory of relativity by observing a solar eclipse in Sobral, Ceará, he told the press: “The problem that my mind posed was answered by the shining sky of Brazil.” The general theory of relativity, in turn, is the basis of cosmology from which the mysteries of dark energy and dark matter are now born. In Aguiar, Paraíba, a century later, it was time for the “bright skies of Brazil” to re-enter the field to try to solve the problem. Let the construction come and then the first results!

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