How did the Universe transform from a cold, dark homogeneity after the Big Bang into the chaotic glow of the first stars? This mysterious period, known as the Cosmic Dawn, remains one of the most challenging puzzles in astrophysics. The light from those times is extremely faint, making direct study of the first cosmic objects almost impossible. The scientific community puts forward theories, but there is a lack of direct evidence. However, according to an international group of astronomers, we are on the verge of a revolution in our understanding of this era.
Signal from the time of the creation of the Universe
In a new study published in the journal Nature Astronomy, scientists report on the development of a model capable of detecting the mass of the earliest stars in the Universe — the so-called Population III stars. The key is the legendary 21-centimeter radio signal.This signal arose approximately 100 million years after the Big Bang, when the first stars shone in the darkness, filling the Universe with light.
After hundreds of thousands of years of cooling, the Universe was filled mainly with neutral hydrogen. But the first stars, like powerful reactors, emitted light that was energetic enough to reionize this hydrogen. In this process, photons with a characteristic wavelength of 21 cm were emitted. This signal is an unmistakable imprint of the birth of the first structures in the cosmos. Deciphering it means obtaining the key to understanding the Cosmic Dawn.
“This is a unique opportunity to learn how the first light of the Universe emerged from darkness,” emphasizes co-author Anastasia Fialkov from the University of Cambridge.
Pioneering stars
Using data from future powerful instruments such as REACH (the Radio Experiment for the Analysis of Cosmic Hydrogen) and the giant Square Kilometer Array (SKA) being built in Australia, scientists have created a model capable of “extracting” information about the mass of Population III stars from the 21-centimeter signal.
A key discovery in creating the model was that previous studies had underestimated the role of special systems among the first stars — X-ray binaries. In such systems, a black hole or neutron star absorbs matter from a normal companion star, generating intense X-ray radiation. It turned out that these systems were both brighter and more numerous than previously thought.
A new look into the depths of time
This work represents a significant step forward in radio astronomy. Recent progress is already beginning to reveal the “low brightness” Universe to us. The model promises to shed unprecedented light on the Cosmic Dawn.
Future observations with REACH and SKA, interpreted using this new model, may finally reveal the first building blocks of our Universe, completing a cosmic mystery that has lasted more than 13 billion years.
Earlier, we reported on how the exact time of the dispersion of the initial hydrogen in the Universe was determined.
According to Phys
