South African telescope detects record-breaking signal from the early universe

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Astronomers using the MeerKAT radio telescope in South Africa have discovered the most distant hydroxyl megamaser ever detected, opening a new radio astronomy frontier. A hydroxyl megamaser is a natural space laser, and this one is located in a violently merging galaxy more than 8 billion light-years away.

We spoke to the astronomers, Thato Manamela, a postdoctoral researcher at the University of Pretoria, and Roger Deane, director of the Inter-University Institute for Data Intensive Astronomy and a professor at the universities of Cape Town and Pretoria, about their study.

What you've found has been described as a 'new frontier' in space research. Why is it extraordinary?

This discovery is extraordinary because of the record distance at which we've detected it, over eight billion light-years away. That places it deep into the early universe. This means that we aren't seeing the galaxy as it exists today. We are seeing it as it was 8 billion years ago. Since the Big Bang happened about 13.8 billion years ago, we are looking at a “toddler” version of the universe. At that stage where the maser signal was transmitted by the host galaxy, galaxies were much more “chaotic”, they collided more often and were much more active than the stable, mature galaxies we see nearby today.

It gives us a rare glimpse of galaxy interactions and extreme star-forming environments when the cosmos was less than half its current age. Think of light like a letter in the mail. If a friend sends a letter from overseas, by the time you read it, the news is old. In space, light is the letter. The “news” from this galaxy took 8 billion years to reach us. We see the galaxy as a “toddler” even though, in its own time, it has already grown up or changed.

We detected this megamaser, which operates on a scale of power millions of times greater than a typical galactic maser. Both megamasers and gigamasers are cosmic radio lasers. While a megamaser is a million times more luminous than a standard maser found in the local universe, a gigamaser is a billion times more luminous, making it 1,000 times more powerful than a megamaser.

In just five hours of observing time we found a signal that typically requires hundreds of hours of observation, given its distance and rarity. But gravitational lensing boosted the signal enough to detect it. Additionally, while we were targeting neutral hydrogen, MeerKAT's wide bandwidth enabled the surprise discovery of the megamaser signal in the same data.

This rapid detection suggests that future surveys with MeerKAT and the upcoming SKA Observatory could uncover many more such distant, extreme objects. Its ability to find this so quickly proves that we finally have the technology to see faint signals from the very distant past. It's a preview of what the upcoming Square Kilometre Array (SKA), a unique, one-of-a-kind international mega-project, might achieve.

But a highly complementary next-generation facility called the next-generation Very Large Array (ngVLA) is being planned and designed for construction in the US. The SKA Observatory (SKA-Low and SKA-Mid) focuses on low-to-mid radio frequencies. The ngVLA will operate at much higher frequencies. Together, they will form two of the major pillars of next-generation global radio astronomy. The finding gives astronomers a new way to study how galaxies evolved in the early universe.

What technologies or capabilities made this possible?

The discovery was made possible by the sensitivity and wide frequency coverage of the MeerKAT radio telescope. Its ability to detect faint signals over a broad frequency range allows us to search for spectral lines across large cosmic volumes. A spectral line is a cosmic chemical fingerprint. Every atom or molecule emits electromagnetic waves at specific frequencies. Detecting those frequencies tells astronomers what the gas is made of.

In this case, MeerKAT's wide bandwidth allowed us to detect both the hydroxyl line and neutral hydrogen absorption in a single observation. Previously, with older technology, this would have taken two separate observations.

Equally important are advances in data processing and computing. The data were processed using high-performance computing resources at the Inter-University Institute for Data Intensive Astronomy (IDIA).

Processing such massive amounts of data is like trying to drink from a firehose. MeerKAT collects gigabytes of information every second, resulting in files far too large for a standard computer to handle. To find a signal from 8 billion years ago, which is millions of times fainter than a cell phone signal, we must use robust calibration pipelines. These act like an automated high-tech car wash to scrub away digital noise and sharpen the telescope's focus. This “cleaning” process requires trillions of mathematical calculations, necessitating the use of supercomputers that work for days to transform raw radio interference into a clear scientific discovery.

Gravitational lensing also played a key role. A massive foreground object, like a star or galaxy, for example, amplified the signal from the distant galaxy, effectively acting as a natural telescope and boosting our ability to detect it.

How does what you've found change our understanding of the universe?

It's rare that a single astrophysical system, a collection of celestial objects, in this case, two galaxies forming a lens system, can change our understanding of the universe. We typically need large sample sizes to do that. But the combination of the recording-breaking distance and the speed of the discovery was impressive.

It suggests that systematic searches – such as those conducted by deep MeerKAT surveys – could convert these once-rare finds into powerful probes of extreme, yet highly obscured star formation in the distant universe. As a result of this observation, the SKA Observatory and other future telescopes won't just be looking for more of the same; they will be looking for hidden history.

Hydroxyl megamasers are usually associated with galaxy mergers. We expect some galaxy mergers to host pairs of supermassive black holes. Almost every large galaxy has a supermassive black hole at its centre. When galaxies merge, the supermassive black holes at their centres can eventually spiral towards each other, producing gravitational waves, ripples in space-time. Finding systems like this helps astronomers study an important stage in galaxy evolution and the environments where these extreme events occur.

By using megamasers to find these pairs, we can study the final stages of how the largest objects in the universe are built. This is a major milestone in a galaxy's life. By finding these galaxies now, we are catching them at a key evolutionary stage, the final countdown before they collide and release a massive burst of energy that our next generation of detectors will be able to hear.

The strength of the MeerKAT-detected hydroxyl signal after such a short observation time therefore implies that astronomers will be able to detect large numbers of these systems across most of cosmic time.

What does the discovery say about South Africa's place in data-intensive radio astronomy?

This discovery highlights South Africa's leading role in radio astronomy. Facilities such as MeerKAT, combined with data-intensive platforms like IDIA, provide world-class capabilities for both observation and analysis. It also demonstrates strong local expertise in handling large, complex datasets.

Discoveries like this rely on advanced data processing, signal extraction and scientific interpretation. These are all key strengths within the South African research community. As we move from using current scout telescopes like MeerKAT to building and operating the world's largest radio observatory, the SKAO, South Africa is well positioned to remain a hub for data-intensive astronomy. Results like this reinforce the country's role in shaping the future of the field.

Thato Manamela works for the University of Pretoria. He receives funding from the National Research Foundation (NRF SARAO). He is affiliated with UP and IDIA.

Roger P. Deane previously held an SKA Research Chair in Radio Astronomy, funded by the South African Radio Astronomy Observatory, which is a facility of the National Research Foundation (NRF), an agency of the Department of Science, Technology and Innovation (DSTI).

By Thato Manamela, South African Radio Astronomy Observatory (SARAO) post-doctoral researcher, University of Pretoria And

Roger P. Deane, Director: Wits Centre for Astrophysics; SKA Chair in Radio Astronomy, University of the Witwatersrand