Astronomers using South Africa’s MeerKAT radio telescope have detected hydrogen signals from 4-5 billion years ago, marking a breakthrough in cosmology. The study, published in The Astrophysical Journal Letters, uses hydrogen intensity mapping to create 3D maps of the universe’s structure, offering new insights into galaxy evolution and dark matter distribution.
The detection of hydrogen gas from the early universe represents a major leap in cosmological research, enabling astronomers to map the large-scale structure of the cosmos with unprecedented precision. Using the MeerKAT radio telescope, a team of scientists analyzed 96 hours of observations, isolating signals from hydrogen atoms that date back 4 to 5 billion years. This achievement, described as a very exciting milestone
by team leader Dr. Sourabh Paul, paves the way for deeper understanding of how galaxies formed and evolved.
Hydrogen Intensity Mapping: A New Window on the Cosmos
The technique of hydrogen intensity mapping relies on detecting the 21-centimeter line, a faint radio signal emitted by neutral hydrogen. As the universe expands, this signal is stretched, allowing astronomers to determine its origin in time and space. “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,” Paul said in a statement. The MeerKAT observations, however, demonstrate that this method is becoming a practical tool for cosmology.
The team’s findings, published in the July edition of The Astrophysical Journal Letters, reveal hydrogen spanning distances of several million light-years—similar to the distance between the Milky Way and Andromeda. Neutral hydrogen is one of the key ingredients for understanding how galaxies form and evolve,
said Dr. Zhaoting Chen, co-author of the study. 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.
The MeerKAT Observations: 96 Hours of Data Yield Cosmic Insights
The research team analyzed 96 hours of MeerKAT data, collected from the telescope’s 64 antennas in South Africa’s Northern Cape. The study focused on hydrogen signals from two distinct epochs in the universe’s history, with the data dating back to a time when the cosmos was significantly younger. 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 Mario G. Santos of the University of the Western Cape. It is particularly remarkable that the data used in this study were taken in 2018, when MeerKAT had only just started science operations.
Traditional methods of hydrogen detection required combining radio data with optical surveys of galaxies. This study, however, marks the first time hydrogen intensity mapping has been achieved using radio observations alone. 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 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.”
Implications for Future Surveys and the SKAO
The Square Kilometre Array Observatory (SKAO), currently under construction in Western Australia and South Africa, is expected to benefit significantly from this advancement. Future cosmological surveys could greatly benefit from the advancement of hydrogen mapping,
Paul said.
The SKAO, which will be the world’s largest radio telescope project, aims to build on the success of MeerKAT. There is now a rich trove of MeerKAT data waiting to be explored with this method,
said Santos. The team plans to conduct longer observations over larger areas of the sky to refine hydrogen maps and uncover more details about the universe’s structure. The team will now focus on collecting further observations with MeerKAT that cover larger areas of the sky over longer periods of time,
Paul added. This should provide astronomers with even more detailed hydrogen maps that could, in time, help understand how the largest structures in the cosmos took shape.
Challenges and Next Steps in Hydrogen Mapping
Despite the success, extracting the hydrogen signal remains a complex task. Foreground radio emissions, human-made interference, and instrumental effects all swamp the delicate hydrogen line,
said Santos. The team’s ability to isolate the signal from 2018 data highlights the potential of MeerKAT’s capabilities. The fact that this signal can be extracted from observations not originally designed for hydrogen intensity mapping is very encouraging,
Wolz said.
Looking ahead, the researchers aim to expand their work by analyzing more data and improving the resolution of hydrogen maps. The results were published in the July issue of The Astrophysical Journal Letters,
noted the team. “Future observations of larger areas of the sky and for longer periods of time will enable astronomers to map hydrogen with even greater detail, and with this they hope to find out how galaxies formed, how dark matter shaped the Universe’s huge filaments, and how cosmic evolution progressed over billions of years.”
The detection of ancient hydrogen signals using MeerKAT underscores the telescope’s growing role in cosmological research. As the SKAO prepares to launch, this breakthrough offers a glimpse into the future of large-scale cosmic mapping and the potential to answer fundamental questions about the universe’s structure and evolution.
