Astronomers have directly detected an exceptionally faint radio signal from hydrogen gas billions of light-years from Earth, demonstrating a promising new method for mapping the universe’s large-scale structure. The discovery was made using South Africa’s MeerKAT radio telescope by researchers from the University of Manchester, the University of the Western Cape and other institutions.
The findings, published in The Astrophysical Journal Letters, highlight the potential of hydrogen intensity mapping to help scientists examine vast regions of space more efficiently and study how the universe has changed over billions of years.
How Hydrogen Intensity Mapping Works
Neutral hydrogen naturally produces a weak radio signal called the 21-centimeter line. As the universe expands, that signal is stretched to longer wavelengths, allowing scientists to observe hydrogen from different periods in cosmic history.
Traditional surveys often attempt to identify individual galaxies. Hydrogen intensity mapping takes a different approach by measuring the combined radio emissions of hydrogen from many galaxies that cannot be resolved separately.
By collecting these signals across large areas of the sky, researchers can construct a three-dimensional picture of the universe and trace the distribution of galaxies and matter over enormous distances.
Until now, dependable detections of this signal at such distances typically required astronomers to combine radio telescope data with optical galaxy surveys. In the latest study, however, researchers detected the hydrogen intensity mapping signal directly using MeerKAT radio observations alone.
Signal Traveled Billions of Years to Reach Earth
The team examined approximately 96 hours of MeerKAT observations. Researchers identified the hydrogen signal from two periods of cosmic history, representing emissions that traveled roughly four billion to five billion years before reaching Earth.
The measurements trace hydrogen across distances spanning several million light-years. That scale is comparable to the distance separating the Milky Way from the Andromeda galaxy, its nearest large galactic neighbor.
“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 from foreground emission, human-made radio-frequency interference, and instrumental effects. Detecting it directly with MeerKAT shows that this technique is becoming a practical tool for cosmology.”
Researchers Overcome Significant Data Challenges
Detecting the signal required researchers to distinguish it from much stronger sources of radio emission. Those included foreground radiation, interference created by human technology and effects produced by the telescope’s instruments.
“This was a challenging data analysis process, requiring a detailed understanding of the many sources of contamination that can affect such a faint measurement,” Professor Santos added. “It is particularly remarkable that the data used in this study were taken in 2018, when MeerKAT had only just started science operations. There is now a rich trove of MeerKAT data waiting to be explored with this method.”
The discovery could give astronomers a more effective way to measure neutral hydrogen across cosmological distances and investigate how galaxies developed over time.
Dr. Zhaoting Chen, a co-author of the study, said, “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. 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.”
MeerKAT Discovery Supports Future Cosmic Surveys
The detection also has implications for future cosmological research using the Square Kilometre Array Observatory, or SKAO. MeerKAT is considered a precursor telescope to the international observatory, and hydrogen intensity mapping is expected to become an important part of SKAO’s scientific mission.
Professor Laura Wolz, a co-author from the University of Manchester, said, “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.”
Larger Surveys Could Map the Cosmic Web
Researchers expect that longer observations covering wider areas of the sky will allow scientists to map neutral hydrogen with greater precision. Those surveys could provide new evidence about galaxy formation, the role of dark matter in shaping the cosmic web and the evolution of the universe.
MeerKAT’s direct detection demonstrates that hydrogen intensity mapping is moving closer to becoming a practical tool for modern cosmology. With additional observations and more advanced telescopes, the method could significantly expand scientists’ understanding of how matter has been distributed throughout cosmic history.
Abigail Prescott is a contributor to Campuslately.com, covering a wide range of topics including news, politics, business, technology, sports, entertainment, and lifestyle. She focuses on delivering clear, accurate reporting and useful information that helps readers stay informed about current events and emerging trends. With a reader-first approach, Abigail highlights stories that matter, providing balanced coverage and accessible insights on issues relevant to everyday audiences.
