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Scientists detect signals of hydrogen from billions of years ago. Could this help us map out the universe?
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Astronomers have achieved a major breakthrough by directly detecting faint hydrogen signals from a period four to five billion years ago using South Africa's MeerKAT radio telescope. This milestone, led by team leader Sourabh Paul, validates a long-theorized technique called hydrogen intensity mapping as a practical tool for cosmology. The achievement promises a more efficient way to chart the large-scale structure of the cosmos.
Hydrogen intensity mapping works by tracing the faint 21-centimeter radio line emitted by neutral hydrogen, the universe's most abundant element. As the universe expands, this signal is redshifted, allowing scientists to determine its age. Previously, this method required combining radio data with visible-light surveys, but the new research builds a map using radio waves alone.
The team analyzed approximately 96 hours of MeerKAT observations, isolating signals from hydrogen existing when the universe was billions of years younger than its current 13.8 billion-year age. The detected hydrogen spans distances of many million light-years, comparable to the gap between the Milky Way and Andromeda. This represents a significant step forward in the technique's usefulness.
Team member Zhaoting Chen of the University of Edinburgh highlighted the scientific impact. The method allows scientists to measure collective hydrogen signals across vast cosmic volumes without detecting every individual galaxy. This provides a new avenue to study both galaxy evolution and the underlying matter distribution of the universe.
The success has immediate implications for future major observatories. The Square Kilometre Array Observatory (SKAO), now under construction, will benefit greatly from this advance. As team member Laura Wolz of the University of Manchester noted, extracting this signal from data not originally designed for the purpose is encouraging and points the way for SKAO's future observations.
Looking ahead, the research team plans to collect further MeerKAT data covering larger sky areas over longer periods. These efforts are expected to yield even more detailed hydrogen maps. Ultimately, this could help scientists understand how the largest structures in the universe formed and evolved over cosmic time.
