MeerKAT Telescope Detects Hydrogen Signal Alone

A team of researchers from the University of Manchester and the University of the Western Cape has, for the first time, pulled an extremely faint neutral hydrogen signal from the distant universe directly out of radio data, with no optical catalog involved at all. The measurement was made with the MeerKAT radio telescope in South Africa, and the study was published on September 1, 2026, in The Astrophysical Journal Letters (DOI 10.3847/2041-8213/ae808f). The lead author is Sourab Paul of the University of Manchester.

The technique is known as hydrogen intensity mapping. Instead of counting galaxies one by one, it measures the combined radio emission of huge numbers of galaxies that cannot be resolved individually, and uses that to build a three-dimensional picture of how matter is distributed across the universe. The signal researchers look for is the so-called 21 centimeter line, the characteristic emission of neutral hydrogen, which shifts toward longer wavelengths as the universe expands. Until now, reliable detections of this signal at large distances have typically required cross-referencing radio data with optical catalogs of galaxies. srpske.rs reported in August on China’s FAST radio telescope and its measurement of hydrogen reserves in a nearby galaxy, where the gas was tracked through a classic radio spectrum of a single observed target. This new result goes a step further: the signal was isolated with no optical anchor whatsoever, straight out of archival radio data.

The team analyzed roughly 96 hours of MeerKAT observations and extracted the signal from two periods in cosmic history, at redshifts of about 0.32 and about 0.44. The light the researchers measured had been traveling toward Earth for between four and five billion years. The underlying data was recorded back in 2018, when MeerKAT had only just begun its scientific operations, well before it was ever designed for this kind of measurement. The measurements were made on spatial scales of a few million light years, roughly the distance between the Milky Way and its neighbor, the Andromeda galaxy. According to the authors, most of the effort went into separating the target signal from foreground emission, human-made radio interference, and effects introduced by the instrument itself.

“This is a very exciting milestone,” said Sourab Paul, the study’s lead author, in a University of Manchester statement. “Hydrogen intensity mapping has long been seen as a promising way to map the universe efficiently, but the signal is extremely weak and difficult to separate from foreground emission, human-made radio interference, and instrumental effects.”

Mario Santos, a professor at the University of the Western Cape and a member of the team, pointed to an unusual detail about where the data came from: “What’s particularly remarkable is that the data used in this study was recorded in 2018, when MeerKAT had only just begun its scientific operations.”

Co-author Zhaoting Chen, who earned his PhD in 2024 and now works at the University of Edinburgh, explained why neutral hydrogen matters for understanding galaxies: “Neutral hydrogen is one of the key ingredients for understanding how galaxies form and evolve.”

MeerKAT is a forerunner of the future Square Kilometre Array observatory, known by the acronym SKA, for which hydrogen intensity mapping is considered one of the main scientific goals. Laura Wolz of the Jodrell Bank Centre for Astrophysics at the University of Manchester, a co-author of the study, tied the result to those plans: “MeerKAT continues to open new windows onto cosmology.”

The result itself, though, remains a demonstration of the method across two narrow slices of cosmic history rather than a map of the whole sky. The analysis covered 96 hours of observations from a single stretch of the telescope’s operation, at just two redshift points, enough to show that the technique works without optical catalogs, but not enough to draw conclusions about dark matter distribution or galaxy evolution across a wider sample. The authors themselves note that only future observations, covering more of the sky and using longer exposure times, will allow more detailed hydrogen mapping and a clearer picture of how the cosmic web has changed over billions of years.