MeerKAT directly detects faint hydrogen signal from the distant universe

The University of Manchester and the University of the Western Cape have directly detected an extremely faint radio signal from hydrogen gas billions of light-years away, using South Africa's MeerKAT radio telescope. The signal, known as the 21-centimeter line, was measured from two periods in cosmic history, corresponding to emissions that traveled for approximately four to five billion years before reaching Earth. The team analyzed around 96 hours of observations from MeerKAT and detected the signal from two periods in cosmic history, corresponding to emissions that traveled for approximately four to five billion years before reaching Earth. The measurements trace hydrogen across scales of several million light-years—comparable to the distance between the Milky Way and its neighboring galaxy, Andromeda.

The findings, published in The Astrophysical Journal Letters, demonstrate the potential of a technique known as hydrogen intensity mapping, which allows astronomers to study vast regions of the cosmos more efficiently than ever before. The team directly detected the hydrogen intensity mapping signal using MeerKAT radio observations alone, overcoming the challenge of isolating the faint signal from foreground emission, human-made radio-frequency interference, and instrumental effects. The study highlights the scientific value of MeerKAT data and points the way to future observations with SKAO. The researchers say the work opens new opportunities to measure neutral hydrogen over cosmological distances and study how galaxies form and evolve over cosmic time.

The detection also has important implications for future cosmological surveys. Hydrogen intensity mapping is expected to become a major science driver for the Square Kilometer Array Observatory, for which MeerKAT is a precursor telescope. Professor Laura Wolz, co-author of the study from the University of Manchester, added, "MeerKAT continues to open new windows for cosmology. The fact that this signal can be extracted from observations that were not originally designed for hydrogen intensity mapping is very encouraging. It shows the enormous scientific value of MeerKAT data and points the way to future observations with SKAO." The researchers say future observations covering larger areas of the sky and using longer observing times will enable astronomers to map hydrogen in even greater detail, helping reveal how galaxies formed, how dark matter shapes the cosmic web, and how the universe has evolved over billions of years.

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