New findings from the University of Bonn challenge the assumptions of the standard cosmological model.
The faint “afterglow” that fills the universe has long been one of the most important clues supporting the Big Bang theory. Known as cosmic microwave background radiation, this ancient light not only serves as a snapshot of the early universe, but also helps scientists understand how the very first galaxies came to be.
Now, a team of researchers from the Universities of Bonn, Prague, and Nanjing is challenging what we thought we knew. Their new calculations suggest that the strength of this background radiation may have been significantly overestimated. If their findings are confirmed, it could force scientists to rethink some of the most fundamental ideas in modern cosmology.
The results have now been published in the journal Nuclear Physics B.
According to the standard model of cosmology, the universe began 13.8 billion years ago with the Big Bang. In the moments that followed, space, time, and matter burst into existence and the universe expanded rapidly. During the first 380,000 years, it also cooled down enough for electrons and protons to combine into neutral hydrogen atoms.
This milestone allowed light to travel freely through space for the first time, since photons were no longer constantly interacting with matter. That moment marked the birth of the cosmic microwave background radiation, the universe’s original light, still detectable today.
We can still detect this radiation today using highly sensitive telescopes. As it has been traveling to us for almost 13.8 billion years, it provides an insight into the birth and the first few hours of the existence of the universe.
“According to our calculations, however, it could be that this background radiation doesn’t exist at all,” explains Prof. Dr. Pavel Kroupa from the Helmholtz Institute for Radiation and Nuclear Physics at the University of Bonn and Charles University in Prague. “At the very least, we are convinced that its strength has been overestimated.”
A powerful star fire overlays the background radiation
The physicist, together with scientist Dr. Eda Gjergo from the University of Nanjing in China, has been investigating a particular group of galaxies called elliptical galaxies.
“The universe has been expanding since the Big Bang, like dough that is rising,” says Kroupa. “This means that the distance between galaxies is increasing constantly. We have measured how far apart elliptical galaxies are from one another today. “Using these data and taking into account the characteristics of this group of galaxies, we were then able to use the speed of expansion to determine when they first formed.”
It was previously already known that elliptical galaxies were the first galaxies that formed in the young universe. Vast volumes of gas accumulated to give rise to hundreds of billions of stars forming these galaxies.
“Our results now show that this entire process only lasted for a few hundred million years—which is relatively short on a cosmological time scale,” emphasizes Dr. Gjergo. “During this time, the nuclear reactions in these ignited stars were intensely luminous.”
Gjergo and Kroupa have calculated the power of this early star fire. They must have blazed so brightly that we are still able to detect them today.
“Our calculations indicate that some of the cosmic background radiation actually originates from the formation of the elliptical galaxies,” says Gjergo. “This accounts for at least 1.4% of the radiation but could even account for all of it.”
Unevenness leads to the creation of galaxies
Even if it accounts for just 1.4%, this would presumably have huge consequences for the standard model. Measurements carried out over the last few decades have shown that the background radiation is not completely uniform. Instead, there are very small differences in its intensity depending on the direction in which you look.
Researchers have interpreted this observation so far as proof that gas was not uniformly distributed after the Big Bang. Instead, it was slightly less dense in some areas than in others. This is also the reason why galaxies were able to form in the first place: The denser areas acted as condensation points where the gas was compressed under the force of its own gravity to form stars.
Without this uneven distribution of gas, we would probably not even exist. However, the variations in the background radiation that form the basis of this theory are only a few thousandths of a percentage point. The question now is how reliable these measurements can actually be if elliptical galaxies (which are also not uniformly distributed) account for at least 1.4% of the total measured radiation.
