What might sound like a concept plucked from vintage science fiction is, in fact, a reality – and cosmic researchers have now detected the most luminous and remote instance of such phenomena to date.
This ‘cosmic microwave amplifier’, scientifically termed a ‘gigamaser‘, is emanating from a colossal galactic merger occurring approximately 8 billion light-years distant. Within this colossal collision, compressed gaseous material is exciting hydroxyl molecules, prompting them to radiate intense radio waves at a singular wavelength.
The unprecedentedly powerful ‘galactic microwave emitter’ was initially identified by the MeerKAT radio telescope situated in South Africa, aided by the natural amplification provided by gravitational lensing.
“We are observing the radio analogue of a laser originating from a location halfway across the observable universe. Furthermore, during its extensive journey to our detectors, the radio waves undergo additional amplification due to a perfectly aligned, yet unconnected, galaxy positioned in the foreground. This intervening galaxy functions as a cosmic lens, analogous to how a droplet of water on a windowpane distorts light, by distorting the fabric of local space-time with its immense mass,” explained Thato Manamela, an astrophysicist affiliated with the University of Pretoria in South Africa.
“Consequently, we have a radio-emitting laser traversing a celestial telescope before being captured by the exceptionally sensitive MeerKAT radio telescope – an confluence of factors that facilitated this remarkably fortunate discovery.”
Although its literal meaning is not commonly considered today, the term ‘laser’ originated as an acronym. It represents ‘light amplification by stimulated emission of radiation’. However, by substituting ‘light’ with ‘microwave’, one arrives at the term ‘maser.’
Both lasers and masers emerge under comparable cosmic circumstances. The presence of a substantial quantity of atoms or molecules in an elevated energy state, coupled with the propagation of photons possessing a specific energy, is essential. When a photon interacts with an atom or molecule, it can instigate the emission of a second photon at the identical energy level. These newly generated photons then possess the capacity to stimulate the release of additional photons, thereby amplifying the overall emission.
Naturally occurring astrophysical masers can manifest in diverse celestial environments, including comets warmed by stellar proximity, the atmospheres of planets and stars, regions of active star formation, and the remnants of supernovae. More potent emissions, referred to as megamasers, can be generated by significantly more energetic cosmic events, such as the activity of supermassive black holes or the cataclysmic merging of galaxies.
The recently identified instance, cataloged as HATLAS J142935.3–002836, transcends the megamaser classification and enters an even more exclusive dominion known as a gigamaser. These phenomena can exhibit luminosities billions of times greater than those of a standard maser.
The generation of such an immense quantity of energy necessitates an extraordinary energetic source. In this particular scenario, the driving force is the collision and subsequent assimilation of two galaxies. The intense gravitational interplay compresses interstellar gas, triggering a prolific burst of nascent star formation. Photons emitted by these newly formed stars then energize ambient hydroxyl molecules, amplifying their microwave emissions and consequently producing a gigamaser.
The electromagnetic radiation originating from this event has traversed a distance of 7.82 billion light-years to be detected by the MeerKAT radio telescope, eclipsing the prior record of ‘merely’ 5 billion light-years. Its exceptional brightness is also primarily attributable to the magnifying effect of the gravitational lens through which the radiation has passed en route to Earth.
“This significant finding underscores MeerKAT’s considerable capacity for investigating high-redshift hydroxyl megamasers, thereby advancing our comprehension of such phenomena and providing invaluable observational tools for probing various facets of galactic outflows and merger dynamics,” the research team stated in their publication.
