Evrim Yazgin
Cosmos science journalist
A powerful “megamaser” has been detected by the MeerKAT telescope in South Africa. Unlike a visible-light laser (light amplification by stimulated emission of radiation), a maser is the emission of photons with longer wavelengths like microwaves and radio waves.
The “mega” prefix tells us that the maser detected by the MeerKAT survey is of galactic proportions. The megamaser is the most distant ever detected, at around 5 billion light years from Earth.
The maser-emitting object has been nicknamed “Nkalakatha”, an isiZulu word meaning “big boss”. The discovery of Nkalakatha was made by an international team led by Dr Marcin Glowacki, who’s now based at the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR) in Western Australia.
Nkalakatha was observed on the first night of a more than 3,000-hour survey by the MeerKAT telescope.
“It’s impressive that, with just a single night of observations, we’ve already found a record-breaking megamaser,” Glowacki says. “It shows just how good the telescope is.”
Glowacki explains that megamasers are usually created when galaxies collide. When galaxies merge, the gases within them become extremely dense and can stimulate hydroxyl molecules to emit radio-wave photons with 18-centimetre wavelengths.
The MeerKAT survey, called Looking at the Distant Universe with the Meerkat Array (LADUMA), was not intended for observing megamasers. LADUMA’s brief was to look for photons of 21-centimetre wavelength emitted in the early universe by neutral hydrogen, redshifted (stretched) by the expansion of the universe.
A happy accident, the light emitted by the megamaser was also stretched by the expansion of the universe so that its wavelengths elongated to within the range detectable by the MeerKAT telescope array.
Megamaser expert and co-author of the study, the University of Colorado’s Professor Jeremy Darling, says that “MeerKAT will probably double the known number of these rare phenomena”. “Galaxies were thought to merge more often in the past, and the newly discovered hydroxyl megamasers will allow us to test this hypothesis,” he adds.
MeerKAT is a precursor for the Square Kilometre Array – a global project to build the world’s largest radio telescopes working in tandem across the Indian Ocean in WA and South Africa.
Scientists believe that studying hydroxyl masers and hydrogen emissions will help astronomers better understand the evolution of the universe.