Plate Nº 21 · recorded October 10, 2026
Space & AstronomyReported finding
Faint Ancient Hydrogen Signal Detected, Paving Way for 3D Cosmic Maps
Astronomers using South Africa's MeerKAT telescope have directly detected faint hydrogen signals from 4–5 billion years ago, opening a faster route to 3D maps of the Universe.
By Nathan Brooks4 min read744 words
In brief
- The signal traveled approximately 4–5 billion years before reaching Earth.
- The team analyzed about 96 hours of MeerKAT observations, detecting hydrogen at two cosmic epochs (z ≈ 0.32 and z ≈ 0.44).
- Results were published September 8, 2026, in The Astrophysical Journal Letters.
- This is a direct hydrogen intensity mapping detection using MeerKAT radio data alone, without optical galaxy surveys.
- The underlying observations date to 2018, when MeerKAT had just begun science operations.
Astronomers have directly detected an extraordinarily faint hydrogen radio signal that traveled for four to five billion years before reaching Earth — a milestone that could soon let them build far larger 3D maps of the Universe than ever before.
The international team, led by researchers at the University of Manchester and the University of the Western Cape, made the detection using South Africa's MeerKAT radio telescope. They published their results on September 8, 2026, in The Astrophysical Journal Letters.
Rather than identifying galaxies one at a time, the researchers measured the combined radio glow of hydrogen gas across vast stretches of space. This technique, called hydrogen intensity mapping, surveys enormous regions of the cosmos far more efficiently than conventional galaxy surveys.
What exactly did the team detect?
The signal comes from neutral hydrogen — plain hydrogen atoms — in a period when the Universe was several billion years younger than it is today. Neutral hydrogen naturally emits a very weak radio wave known as the 21-centimeter line.
Because the Universe is expanding, that signal stretches to longer wavelengths as it travels through space. Astronomers measure this stretch to determine how far away — and how long ago — the hydrogen is.
The team analyzed roughly 96 hours of MeerKAT observations and found the hydrogen signal from two separate periods in cosmic history. The measurements let them trace hydrogen across distances of several million light-years, comparable to the gap between the Milky Way and the neighboring Andromeda galaxy.
Why is this detection significant?
Previous reliable measurements of hydrogen at these distances generally required astronomers to combine radio telescope data with separate optical galaxy surveys. Here, the researchers identified the hydrogen intensity mapping signal using MeerKAT radio observations alone.
That matters because the signal is extraordinarily weak and easily swamped. The team had to carefully filter out foreground emission from other cosmic sources, human-made radio-frequency interference, and instrumental effects that could distort the measurement.
"This is a very exciting milestone," said Dr. Sourabh Paul, lead author of the study. "Hydrogen intensity mapping has long been seen as a promising way to map the Universe efficiently, but the signal is extremely faint and difficult to isolate. Detecting it directly with MeerKAT shows that this technique is becoming a practical tool for cosmology."
Professor Mario G. Santos, a co-author, highlighted the difficulty of the analysis. "This was a challenging data analysis process, requiring a detailed understanding of the many sources of contamination that can affect such a faint measurement," he said.
How old is the data?
Surprisingly, the observations date back to 2018, when MeerKAT had only just begun science operations. "There is now a rich trove of MeerKAT data waiting to be explored with this method," Santos added.
The fact that the signal could be extracted from observations not originally designed for hydrogen intensity mapping is itself encouraging, according to Professor Laura Wolz of the University of Manchester.
"MeerKAT continues to open new windows for cosmology," Wolz said. "It shows the enormous scientific value of MeerKAT data and points the way to future observations with SKAO."
What does this mean for studying galaxies?
Neutral hydrogen is the raw material from which stars and galaxies form. Measuring it across cosmic time gives astronomers a way to track how galaxies have grown and changed.
Dr. Zhaoting Chen, co-author of the study, explained: "Neutral hydrogen is one of the key ingredients for understanding how galaxies form and evolve."
"With intensity mapping, we do not need to detect every individual galaxy," Chen said. "Instead, we can measure the collective signal from hydrogen across large cosmic volumes, giving us a new way to study both galaxy evolution and the underlying matter distribution of the Universe."
What comes next?
The detection carries implications for upcoming cosmology projects. Hydrogen intensity mapping is expected to become a major scientific focus of the Square Kilometre Array Observatory (SKAO), an international facility for which MeerKAT serves as a precursor telescope.
Future observations covering larger portions of the sky for longer periods should map neutral hydrogen with greater precision. Those maps could help researchers:
- understand how galaxies developed over billions of years;
- determine how dark matter shapes the cosmic web of matter;
- reconstruct how the Universe has changed across cosmic history.
As with any single detection, the findings mark an early step rather than a finished map. Still, they demonstrate that a long-promising technique has crossed the threshold from theory to practical astronomical tool.
via dx.doi.org (Original)
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