An international research team led by scientists at the University of Manchester and the University of the Western Cape has successfully detected a radio signal from neutral hydrogen originating from several billion years in the past. Using data from South Africa’s MeerKAT radio telescope, the researchers identified emissions from hydrogen gas at cosmological distances, marking a significant advancement in observational cosmology. The findings were published in The Astrophysical Journal Letters.
The detection demonstrates the viability of hydrogen intensity mapping, a technique that surveys vast cosmic regions more efficiently than traditional methods requiring the identification of individual galaxies. Neutral hydrogen naturally emits a weak radio signal at a wavelength known as the 21-centimeter line. As the Universe expands, this signal stretches to longer wavelengths during its journey through space, allowing astronomers to study hydrogen from different periods of cosmic history. Rather than measuring galaxies one at a time, intensity mapping detects the combined radio emissions from numerous unresolved galaxies, enabling examination of enormous volumes of space and reconstruction of three-dimensional matter distribution patterns.
Previously, detecting hydrogen at such great distances typically required combining radio telescope observations with optical galaxy survey data. In this study, researchers isolated the hydrogen intensity mapping signal using only MeerKAT radio observations. Analysis of approximately 96 hours of observational data revealed hydrogen emissions that had traveled roughly four to five billion years to reach Earth, allowing the team to trace hydrogen distributions across distances comparable to the separation between the Milky Way and Andromeda galaxy. Extracting such a faint signal required sophisticated data analysis to eliminate interference from various contamination sources, including foreground emissions and radio-frequency interference.
The successful detection opens new research pathways for studying neutral hydrogen across cosmological distances and investigating galaxy formation and evolution. The methodology is expected to become a major scientific focus for the Square Kilometre Array Observatory, with MeerKAT serving as a precursor facility. Future observations covering larger sky areas over extended periods should enable more precise mapping of neutral hydrogen distribution, potentially yielding insights into galaxy development, dark matter’s influence on cosmic structure, and the Universe’s evolution over billions of years.
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