Brightest Distant Space Laser Gigamaser Detected by MeerKAT

Although it may evoke pulpy ’50s science fiction, “space lasers” genuinely exist - and astrophysicists have now identified the brightest and most distant example to date.

The newly found “gigamaser” comes from an enormous galactic merger roughly 8 billion light-years away. There, tightly compressed gas causes hydroxyl molecules to release powerful radio waves at a matching wavelength.

How a gigamaser produces microwave emission

Although it is no longer commonly thought of this way, “laser” originally began as an acronym: “light amplification by stimulated emission of radiation”. Replacing light with microwave produces the term “maser”.

Lasers and masers form in comparable circumstances. They require large numbers of atoms or molecules in an excited state, together with photons travelling around at a particular energy. When one of these photons hits an atom or molecule, it may prompt the release of a second photon at the same energy level. Those newly emitted photons can, in turn, trigger still more emissions, increasing the strength of the signal.

Naturally occurring astrophysical masers are found in settings including star-warmed comets, planetary and stellar atmospheres, regions where stars are forming, and supernova remnants. More energetic phenomena, such as supermassive black holes and colliding galaxies, can generate stronger emissions called megamasers.

The new object, HATLAS J142935.3–002836, exceeds megamaser classification and belongs instead to the still rarer gigamaser category. A gigamaser can shine billions of times more brightly than an ordinary maser.

Creating such an immense energy output needs an extraordinary furnace. In this instance, that power is supplied by two galaxies colliding and merging into one. Their powerful gravitational interaction squeezes the gas and sets off a burst of new star formation. Photons from these newborn stars stimulate nearby hydroxyl molecules, boosting their microwave output and creating a gigamaser.

MeerKAT detects a record-breaking space laser

MeerKAT, the radio telescope in South Africa, detected the record-setting “ginormous microwave laser”, aided by the natural effect of gravitational lensing.

“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,” says Thato Manamela, astrophysicist at the University of Pretoria in South Africa.

“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.”

Light from the event travelled 7.82 billion light-years before reaching MeerKAT, overtaking the previous record distance of “only” 5 billion light-years. It is also the brightest example observed so far, chiefly because the gravitational lens along its route magnifies the signal.

“This discovery highlights MeerKAT's potential to investigate high- redshift hydroxyl megamasers, enhancing our understanding of thereof and offering valuable tracers for exploring different aspects of galaxy outflows and merging activity,” the researchers write.

The research has been accepted by Monthly Notices of the Royal Astronomical Society Letters and is presently available as a preprint.