Researchers at Tel Aviv University have introduced a novel approach to explore the enigmatic “dark ages” of the Universe, a period preceding the formation of the first stars. Their findings, recently published in Nature Astronomy, suggest that hydrogen gas present approximately 100 million years after the Big Bang may have produced faint radio signals shaped by dark matter.
By examining these signals, scientists hope to unlock crucial information about the behavior and distribution of dark matter long before the emergence of galaxies and stars. Led by Professor Rennan Barkana from the Sackler School of Physics and Astronomy, along with Ph.D. student Sudipta Sikder and international collaborators from Japan, India, and the UK, the study indicates that during this cosmic dark age, dark matter formed dense clusters, or “nuggets,” which attracted surrounding hydrogen gas.
This interaction caused the gas to emit radio waves that were unexpectedly strong. Although these signals are incredibly faint, the cumulative effect of numerous such emissions could be detectable with specialized instruments, potentially providing a new method to trace the impact of dark matter.
“Our research focuses on an era even earlier and more mysterious than the one NASA”s James Webb Space Telescope studies,” stated Professor Barkana. “We”re investigating the Universe just 100 million years after the Big Bang—well before the first stars. These radio signals could help us understand how dark matter influenced everything that followed.”
However, detecting these ancient radio waves from Earth poses significant challenges, primarily due to atmospheric interference and the overwhelming noise generated by human activity. This is why researchers advocate for utilizing the Moon, specifically its far side, which is shielded from Earth”s disturbances and lacks an atmosphere, making it an ideal location for sensitive radio antennas.
With various global space agencies, including NASA, ESA, China, and India, planning to return to the lunar surface, scientists see a prime opportunity to construct lunar radio telescopes that could explore the Universe”s earliest epochs.
As the first stars ignited during a phase known as the “cosmic dawn,” their radiation likely amplified the existing radio emissions. While signals from this subsequent era can be more readily detected using ground-based instruments, interpreting these signals is complex due to the additional variables introduced by star formation.
To tackle this challenge, astronomers are working on expansive radio observatories such as the Square Kilometre Array (SKA), a global initiative that plans to deploy tens of thousands of antennas across Australia and South Africa. The SKA aims to map minute fluctuations in cosmic radio brightness, effectively tracing the locations where dark matter once influenced the structure of the young Universe.
Dark matter constitutes the majority of matter in the cosmos, yet its true nature remains one of the greatest enigmas in physics. Its interactions are deeply intertwined with galaxies and stars, complicating efforts to isolate its behavior. Investigating the pristine Universe prior to the formation of these structures may finally reveal the fundamental properties of dark matter.
“Every time astronomers open a new observational window, the Universe surprises us,” remarked Professor Barkana. “If we can detect these ancient radio waves, we may be able to listen to the very first cosmic broadcasts—and, in doing so, uncover the story of dark matter itself.”
