Israeli scientists propose new way to ‘hear’ the universe’s dark matter
Israeli scientists have outlined a groundbreaking method to study dark matter, providing a direct window into the mysterious substance that comprises most of the universe’s matter, Tel Aviv University announced on Monday.
Dark matter is a type of matter that does not emit, absorb, or reflect light, making it invisible to telescopes. Scientists know it exists only because of its gravitational effects on galaxies and the large-scale structure of the universe. It is estimated that about 85% of all matter in the universe is dark matter, yet its composition remains unknown, as no dark matter particle has been directly detected.
The new study, led by Prof. Rennan Barkana of Tel Aviv University’s Sackler School of Physics and Astronomy, proposes detecting faint radio waves emitted during the universe’s earliest period, the cosmic dark ages, about 100 million years after the Big Bang. The research, published in Nature Astronomy, indicates that dark matter formed dense clumps at this early stage, pulling in hydrogen gas and producing weak but measurable radio emissions.
“NASA’s new James Webb Space Telescope recently discovered distant galaxies whose light reaches us from about 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,” Barkana said.
“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 clumps 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, causing 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.”
An international space race
“We are seeing an international space race in which many countries aim to return to the Moon with probes and astronauts,” the study noted. “Space agencies in the US, Europe, China, and India are searching for worthy scientific goals for lunar development, and detecting radio waves from the cosmic dark ages offers a compelling target.”Later periods, such as the cosmic dawn when the first stars formed, are predicted to produce stronger radio signals. These can be measured from Earth, though interpreting them is complicated by the influence of star formation. Barkana is part of the Square Kilometre Array (SKA), an international project deploying 80,000 radio antennas in Australia to map these emissions and trace the fingerprints of early dark matter clumps across the sky. “The radio signal from the cosmic dark ages should be relatively weak, but if the observational challenges can be overcome, it will open new avenues for testing the nature of dark matter,”
Barkana said. “In the present universe, dark matter has interacted with stars and galaxies for billions of years, making it difficult to decode its properties. Observing it in the early universe gives us a pristine laboratory, potentially revealing what dark matter actually is.
Said Barkana, “When scientists open a new observational window, surprising discoveries usually follow. The holy grail of physics is to uncover the properties of dark matter. This research points to a way we may finally do so, tuning into the cosmic radio channels of the early universe and glimpsing the invisible scaffolding on which all galaxies, including our own Milky Way, were built.”
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