A computer simulation has succeeded for the first time in explaining how galaxies that are virtually free of dark matter can appear in the universe, without having to change the standard cosmological model, our best theories to include the evolution of the universe.
The work was first authored by Jorge Moreno, of the California Institute of Technology (USA), and published in Nature Astronomy. It’s undoubtedly a huge relief among enthusiasts of the roundabout version ever formulated about how the universe has turned out the way it is over the last 13.8 billion years.
The so-called Standard Model assumes, in addition to the conventional matter that makes up everything we see, the presence of a certain amount of “cold” dark matter – particles we don’t know what they are, but we have excellent reason to believe they exist, because they emit gravitational – and dark energy, In the form of Einstein’s cosmological constant – something like energy in vacuum itself, on larger scales, works against gravity, accelerating the expansion of the universe.
Building on these introductions, the researchers run a cosmological computer simulation, comparing what theory predicts for the overall appearance of the universe from the Big Bang to today with what we can observe with a telescope. In general, things are going in place very well. But the latest discovery made cosmologists pause without end. Actually two. Two galaxies found in 2018 and 2019 by astronomer Peter van Dekoon of Yale University, classified as DF2 and DF4, appear to contain almost no dark matter.
This was in stark contrast to the Standard Model, where galaxies are born from a great cradle of dark matter, and all simulations run so far seemed to indicate that such an impossibility had occurred. Then a cockroach began to occur in society: will the model be punctured?
So Moreno and his colleagues ran simulations of galactic evolution, using unusually high resolutions for such experiments, and found, yes, that the Standard Model could produce galaxies devoid of dark matter. This apparently happens when smaller galaxies encounter an older sister up close. There is the dark matter, because it rotates more easily, it ends up separating it from the mass of gas and stars. Incidentally, this should be the case for DF2 and DF4, which are satellites of the galaxy NGC 1052.
In addition to saving our better understanding of the universe from an embarrassing failure, the new simulation offers a prediction: 30% of large central galaxies with 100 billion or more suns have at least one satellite galaxy with 100 million billion suns defective in dark matter. That is, the ball is now back in the court of observational astronomers, who need to find more galaxies like DF2 and DF4 to confirm the new claim emerging from the model.
This column is published on Monday in Folha Corrida.
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