Radio Signal from Early Universe May Reveal the Masses of the First Stars

A faint radio signal beamed over the eons by hydrogen atoms in the early universe that contains important information about the mass and nature of the first stars. The finding is made by researchers, including those from the University of Cambridge, using a new model that for the first time investigates the effects of early starlight, which is produced by the first generation of stars, and the impact of the first supernovae on the 21-centimetre line from hydrogen. The finding gives us a new approach to learn about the Cosmic Dawn, a time when the cosmos changed from dark to light through the formation of stars and galaxies.

Early Universe's Radio Signal Reveals Mass of First Stars, Say REACH and SKA Researchers

According to a report in Nature Astronomy, the team—including Professor Anastasia Fialkov from Cambridge's Institute of Astronomy—demonstrated that the 21-cm signal, originating just 100 million years after the Big Bang, is sensitive to the masses of the first stars. These Population III stars are thought to be vastly different from stars today, and their influence on hydrogen gas could be tracked through radio observations. The work was conducted under the REACH project and contributes to the upcoming Square Kilometre Array (SKA).

Instead of visual observation like that performed by the James Webb Space Telescope, the REACH and SKA instruments collect statistical data about cosmic radio waves. In addition, they considered the impact of ultraviolet light and X-rays — produced by X-ray binary systems — on the 21-cm signal. They discovered that the impact of these factors on early cosmic rays had been underestimated in earlier studies, especially for what happens when collapsed stars interact with surviving stars in binary systems.

Though still in its calibration phase, REACH is already offering insights into the universe's first billion years. Fialkov and her team think the technique might eventually determine not only when stars were forming but also how massive they were. “The outcomes of this project will define the future of radio astronomy, including site involvement from places such as the Karoo (South Africa),” explains Dr Eloy De Lera Acedo, REACH principal investigator.

These findings are a significant step toward understanding how the first objects in the universe developed from darkness to a galaxy.