Astronomers using South Africa’s MeerKAT radio telescope have detected a faint hydrogen signal from 4 to 5 billion years ago, marking a breakthrough in mapping the universe’s large-scale structure through hydrogen intensity mapping, according to multiple outlets including Sciencedaily, TodayPress.tv, Space, and Xinhua.
The detection, achieved by analyzing 96 hours of MeerKAT data from 2018, represents a critical step in cosmology. Neutral hydrogen, the universe’s most abundant element, emits a 21-centimeter radio signal that shifts due to cosmic expansion. By isolating this faint emission, researchers can trace hydrogen across vast distances without individually identifying galaxies, a method known as hydrogen intensity mapping.
A Faint Signal, A Major Achievement
Dr. Sourabh Paul, lead author of the study, described the detection as a very exciting milestone,
noting that hydrogen intensity mapping has long been considered a promising tool for cosmology. The signal, which traveled 4 to 5 billion years to reach Earth, was extracted from observations not originally designed for this purpose. This was a challenging data analysis process, requiring a detailed understanding of the many sources of contamination that can affect such a faint measurement,
said Professor Santos of the University of the Western Cape.
The team identified emissions from two cosmic epochs, corresponding to redshifts of 0.32 and 0.44. These signals spanned distances of several million light-years, comparable to the space between the Milky Way and Andromeda. Neutral hydrogen is one of the key ingredients for understanding how galaxies form and evolve,
added Dr. Zhaoting Chen, a co-author of the study. By measuring the collective hydrogen signal, astronomers can study galaxy evolution and matter distribution without the need to detect individual galaxies.
The success highlights MeerKAT’s potential as a precursor to the Square Kilometre Array Observatory (SKAO), which is set to begin operations around 2028. MeerKAT continues to open new windows for cosmology,
said Professor Laura Wolz of the University of Manchester. The fact that this signal can be extracted from observations that were not originally designed for hydrogen intensity mapping is very encouraging.
Implications for Cosmological Surveys
The findings could transform how astronomers map the universe. Traditional methods rely on combining radio data with optical galaxy surveys, but this study demonstrates that hydrogen intensity mapping can work independently. This direct detection with MeerKAT shows that the method is becoming a practical tool for cosmology,
Paul said.
The technique’s efficiency lies in its ability to survey vast cosmic volumes. Instead of tracking individual galaxies, researchers measure the cumulative radio glow from hydrogen in unresolved galaxies. This approach allows for a three-dimensional view of matter distribution, which is critical for studying the universe’s expansion. There is now a rich trove of MeerKAT data waiting to be explored with this method,
Santos noted.
The results also underscore the value of existing data. The 2018 observations, taken when MeerKAT was still in its early science phase, yielded a signal that could now be analyzed with advanced techniques. It is particularly remarkable that the data used in this study were taken in 2018,
Wolz said. There is now a rich trove of MeerKAT data waiting to be explored with this method.
Looking Ahead: The Role of SKAO and MeerKAT
The Square Kilometre Array Observatory (SKAO), currently under construction in Australia and South Africa, will build on MeerKAT’s capabilities. Future studies that observe larger portions of the sky for longer periods should allow astronomers to map neutral hydrogen with even greater precision,
the researchers wrote in their study published in The Astrophysical Journal Letters.
MeerKAT’s 64-dish array, located in South Africa’s remote Karoo region, has already proven its scientific value. The telescope’s ability to extract faint signals from early data suggests that its full dataset holds untapped potential. Gasant Abader, a spokesperson for the University of the Western Cape, told Xinhua about the findings. It points the way to future observations with SKAO.
As SKAO prepares for its 2028 launch, the lessons from this study will inform its design and operations. The ability to map hydrogen intensity without relying on optical surveys could streamline cosmological research, offering a faster and more efficient way to chart the universe’s structure. For now, the detection of this ancient hydrogen signal stands as a milestone in humanity’s quest to understand the cosmos.
