Astronomers using South Africa’s MeerKAT radio telescope have detected an extraordinarily bright hydroxyl (OH) megamaser more than 8 billion light‑years from Earth, the South African Radio Astronomy Observatory announced. The emission originates in a merging galaxy catalogued as HATLAS J142935.3‑002836 and — aided by strong gravitational lensing — is both the most distant and the most luminous OH megamaser observed to date.
OH megamasers are rare, intensely luminous radio signals produced when hydroxyl molecules in the dense, warm molecular gas of a galaxy are pumped by intense infrared radiation from starbursts or active galactic nuclei. Because they trace copious molecular fuel and vigorous star formation in gas‑rich mergers, OH megamasers are valuable signposts for studying the processes that drive galaxy growth and black‑hole feeding across cosmic time.
That value has been hard to exploit at large distances: maser emission is intrinsically faint and traditionally limited to the relatively nearby universe. The combination of MeerKAT’s sensitivity and the amplification provided by a foreground gravitational lens has overcome that barrier in this case, bringing into view a signal from a system whose light left the universe when it was substantially younger.
The discovery matters for two complementary reasons. First, it demonstrates that current radio facilities can detect molecular tracers of star formation at epochs approaching the peak of cosmic star formation, offering a new window on how the most intense starburst and merger events unfolded. Second, it validates a strategy of using lensing to extend the reach of radio surveys: nature’s telescopes can turn otherwise undetectable sources into bright, studyable targets.
MeerKAT — itself a precursor to the Square Kilometre Array (SKA) — has been steadily delivering discoveries that showcase the coming era of wide, deep radio surveys. Identifying an OH megamaser at such distance suggests that systematic searches with MeerKAT and, later, the SKA could assemble sizable samples of distant molecular masers. Those samples would help calibrate relations between infrared luminosity, molecular gas content and maser luminosity, and they would provide complementary redshift measurements for highly obscured systems that are difficult to study at optical wavelengths.
Follow‑up observations will be needed to convert a single striking detection into scientific leverage. High‑resolution interferometry could pin down the maser’s spatial structure and separation between the merging nuclei, while submillimetre and infrared facilities can measure the host’s gas mass, star‑formation rate and the degree of lensing magnification. Together, such data will clarify whether the extreme brightness is intrinsic or dominated by lensing and will place the source in the broader context of galaxy evolution at intermediate redshifts.
For astronomy in South Africa and the wider radio community, the finding is also symbolic. It highlights MeerKAT’s role as a world‑class instrument able to push molecular and dynamical studies into regimes previously reserved for optical and submillimetre telescopes. As the SKA era approaches, discoveries like this one foreshadow a dramatic expansion in the number and distance of extragalactic molecular tracers available to astronomers, improving our ability to chart when and how galaxies assembled their stars and central black holes.