By Murilo Bomfim
In astroparticle physics, discoveries arise from what we cannot see
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Anyone who has gazed at a star-studded sky has thought about these points of light. Maybe look for the Três Marias or try to understand if a particular little light is a star or a planet. It is less common to wonder about the dark area in which the stars float.
Today we know that this area is not a great emptiness. It has matter, this dark matter. One of the great challenges facing science is to decipher the composition of the particles in this matter, a task that is made more difficult precisely by the fact that these particles do not emit light. In other words, we cannot see them.
A better understanding of dark matter creates space for a revolution in science. Physics has a standard model for elementary particles that explains the behavior of all particles … except dark matter particles. Unraveling the mystery can give new directions to science, especially in the fields of cosmology, astronomy, and astrophysics.
Only a few researchers worldwide have dealt with this topic. One of them was the Brazilian Farinaldo Queiroz.
When Francisco Farinaldo Queiroz’s son entered physics at the Federal University of Paraíba in 2002, the academic world seemed a dark matter to him. “At first I thought I wouldn’t graduate. When I saw a six credit course, I didn’t understand that it was an indication of workload. I thought it would cost six reais per semester or per class, which would be hard to pay, ”he recalls.
As he graduated, everything became clearer: he understood what credit points are and learned about particle physics when he got an introductory scholarship in the field. He soon found pleasure in the topic and deepened his master’s and doctoral studies – with the right to receive an award from the Brazilian Society for Physics as the best thesis in 2013.
At that time, the scientist had a discovery that marked the beginning of his meteoric trajectory. It is known that for every particle there is an antiparticle – with properties similar to mass, but opposite properties to electrical charge. When particles and antiparticles collide, which happens randomly, photons (or gamma rays) are emitted.
Queiroz understood in his studies that if it were possible to capture a signal from these photons, there would be a high probability that the dark matter particles were of a certain type, called WIMPs (Weakly Interacting Massive Particles).
The physicist managed to capture a beam, and the work was successful. But the result is just a good hypothesis. With limited research opportunities in the country, he was pursuing a postdoctoral degree from the University of California. His desire to unravel dark matter earned him money from NASA, which eventually opened the doors for him to research and teach at European universities.
After observing the universe from other countries, the physicist was chosen to work as a scientist in a place much closer to his Paraíba origins: the Federal University of Rio Grande do Norte.
However, the ambitions remain astronomical. Today he is one of the few in the world who is trying to decipher the peculiarities of dark matter using the specific method of analyzing neutron stars. These stars, which are found in multiple galaxies, have a greater mass than those of the Sun, but they have a much smaller radius.
This high density creates a strong gravitational field, which means that everything that goes through a neutron star is swallowed. Coincidentally, its temperature gradually decreases over the life cycle of the star. Should there be an increase, Queiroz and his colleagues bet on the entry of dark matter particles into the stars. By measuring the temperature, conclusions can be drawn about the nature of the particles.
The idea is exciting and challenging. Mainly because it requires multidisciplinary work: Queiroz understands particle physics, but he needs someone who understands astrophysics and astronomy (for example, to measure the temperature of neutron stars).
“We compete with other international groups to see who arrives first,” says the scientist. “If we can do that, you will see us at the Nobel Prize ceremony.”
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Murilo Bomfim is a journalist.
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