Researchers at Tel Aviv University have proposed detecting faint radio waves from the cosmic dark ages to uncover dark matter's properties. These signals, emitted by hydrogen gas influenced by dark matter clumps just 100 million years after the Big Bang, could be best observed from the Moon. The findings, published in Nature Astronomy, highlight a new method to probe the Universe's earliest moments.
In a study led by Prof. Rennan Barkana from Tel Aviv University's Sackler School of Physics and Astronomy, along with Ph.D. student Sudipta Sikder and collaborators from Japan, India, and the United Kingdom, scientists predict that radio waves from the cosmic dark ages hold clues to dark matter. This era, occurring just before the first stars formed around 100 million years after the Big Bang, saw dark matter forming dense clumps that pulled in hydrogen gas, causing it to emit stronger radio signals.
Prof. Barkana explained: "NASA's new James Webb space telescope discovered recently distant galaxies whose light we receive from early galaxies, around 300 million years after the Big Bang. Our new research studies an even earlier and more mysterious era: the cosmic dark ages, only 100 million years after the Big Bang. Computer simulations predict that dark matter throughout the Universe was forming dense clumps, which would later help form the first stars and galaxies. The predicted size of these nuggets depends on, and thus can help illuminate, the unknown properties of dark matter, but they cannot be seen directly. However, these dark matter clumps pulled in hydrogen gas and caused it to emit stronger radio waves. We predict that the cumulative effect of all this can be detected with radio antennas that measure the average radio intensity on the sky."
Earth's atmosphere blocks these faint signals, making space-based observations essential, particularly on the Moon's radio-quiet surface free from human interference. With missions from the United States, Europe, China, and India racing back to the Moon, lunar telescopes could enable this research.
The study suggests these signals, amplified during the cosmic dawn when first stars ignited, could be detected by projects like the Square Kilometre Array (SKA), an international effort with 80,000 antennas under construction in Australia. Prof. Barkana, involved in SKA, noted: "Just as old radio stations are being replaced with newer technology that brings forth websites and podcasts, astronomers are expanding the reach of radio astronomy. When scientists open a new observational window, surprising discoveries usually result. The holy grail of physics is to discover the properties of dark matter, the mysterious substance that we know constitutes most of the matter in the Universe, yet we do not know much about its nature and properties. Understandably, astronomers are eager to start tuning into the cosmic radio channels of the early Universe."
This approach offers a pristine view of dark matter before galaxies formed, potentially transforming our understanding of cosmic evolution. The research was published in Nature Astronomy.