MeerKAT discovers record-breaking cosmic laser halfway across the universe

University of Pretoria-led team opens a new frontier using the power of MeerKAT and strong gravitational lensing

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

Hydroxyl megamasers are natural “space lasers” – extremely bright radio-wavelength emissions produced when hydroxyl molecules in gas-rich, merging galaxies crash into one another. These cosmic collisions compress gas and stimulate large reservoirs of hydroxyl molecules to amplify radio emission. The physical mechanism is very similar to lasers on Earth, but operates at a much longer wavelength of light of about 18 centimetres, rather than optical light that our eyes can see.  When this special radio light is exceptionally bright, it is termed a megamaser – a “cosmic beacon” that can be seen across vast stretches of the Universe.

This newly discovered system, HATLAS J142935.3–002836, is so distant that we are seeing it as it was when the Universe was less than half its present age. It is both the most distant and luminous known. In fact, it is so luminous that it warrants the classification gigamaser, instead of megamaser. Despite its distance, it produced a surprisingly strong signal, which is thanks to the combined power of MeerKAT and a phenomenon known as strong gravitational lensing, which was theorised by Einstein.

“This system is truly extraordinary,” said Dr Thato Manamela, SARAO-funded postdoctoral researcher at the University of Pretoria and lead author of the new study. “We are seeing the radio equivalent of a laser halfway across the universe. Not only that, during its journey to Earth, the radio waves are further amplified by a perfectly aligned, yet unrelated foreground galaxy. This galaxy acts as a lens, the way a water droplet on a window pane would, because its mass curves the local space-time. So we have a radio laser passing through a cosmic telescope before being detected by the powerful MeerKAT radio telescope – all together enabling a wonderfully serendipitous discovery.”

Illustration of the distant galaxy 8 billion light-years away (red), magnified by an unrelated foreground disk galaxy, resulting in a red ring. Splitting up the radio light into different colours, as a prism does, reveals the hydroxyl gigamaser (top-right rainbow-coloured line). Image Credit: Inter-University Institute for Data-Intensive Astronomy (IDIA)

MeerKAT’s design makes it exceptionally well-suited to detect faint radio emission at centimetre wavelengths. However, collecting the data is only part of the challenge – astronomers must carefully calibrate and analyse terabytes of information using sophisticated algorithms and scalable computing platforms, before any breakthrough discoveries are possible.

“This result is a powerful demonstration of what MeerKAT can do when paired with advanced computational infrastructure, fit-for-purpose data processing pipelines, and highly-trained software support personnel,” said Prof Roger Deane, co-author of the study and Director of the Inter-University Institute for Data Intensive Astronomy (IDIA), as well as Professor at the Universities of Cape Town and Pretoria. “This synergistic combination empowers young South African scientists, like Dr Manamela, to lead cutting-edge science and compete with the best in the world.”

Hydroxyl megamasers are a rare phenomenon. Previous studies showed they trace the most vigorous galaxy collisions, where enormous reservoirs of gas fuel intense starbursts and feed central black holes. Systematic searches – such as those conducted by deep MeerKAT surveys – promise to convert these once-rare finds into powerful probes of cosmic evolution.

“This is just the beginning,” said Dr Manamela. “We don’t want to find just one system – we want to find hundreds to thousands. Here at the University of Pretoria, we are carrying out systematic surveys of the universe, building the required computational pipelines and algorithms to open this observational frontier ahead of, and ultimately with the Square Kilometre Array.”

The discovery underscores South Africa’s growing leadership in data-intensive radio astronomy, driven by the strong partnership between IDIA and SARAO to deliver MeerKAT science and prepare for the SKA era.

The paper was accepted for publication in Monthly Notices of the Royal Astronomical Society Letters, and the pre-print can be accessed at this link: https://arxiv.org/abs/2602.13396.

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