Astronomers have discovered a supercharged space laser firing at Earth from halfway across the universe. The cosmic energy ray, revealed to us in part via a strange space-time trick first predicted by Einstein, is the brightest and most distant of its kind ever seen.
The natural laser, called a “hydroxyl megamaser” is essentially a giant beam of electromagnetic radiation emitted when a pairs of galaxies violently merge. During these cosmic collisions, giant clouds of gas are compressed, exciting large reservoirs of hydroxyl (OH) molecules that release high-energy microwaves.
This is similar to man-made laserswhich works by exciting particles and then amplifying the resulting light waves with mirrors. But for masers, microwaves are amplified instead of visible light – hence the “M” at the beginning of the name. (Laser is an acronym for “light amplification by stimulated emission of radiation”; replace “light” with “microwave” and you’ve got a maser.)
Scientists are particularly interested in megamasers because they can shed light on how ancient galaxies form, grow, evolve and die. As a result, they are often called “cosmic beacons”.
In a new study, uploaded February 13 to the preprint server arXiv and accepted for future publication in the journal Monthly Notices of the Royal Astronomical Society: Letters, researchers using the MeerKAT telescope – an array of 64 radio dishes located in South Africa – discovered a new hydroxyl megamaser coming from a pair of colliding galaxies called HATLAS J142935.36–002.
The microwaves fired by this system are very stretched, around 18 centimeters in length (7 inches or 1665 megahertz), and are so much brighter than other megamasers that the researchers have proposed that the signal should be classified as a “gigamaser” – the next theoretical order of magnitude for these space lasers.
HATLAS J142935.3–002836 var first discovered in 2014 and is about 8 billion light-years from Earth, meaning that the microwaves we see were emitted when the universe was about half its current age. This makes it comfortably the most distant megamaser seen to date.
“This system is truly extraordinary,” studied first author It’s Manamelaan astronomer at the University of Pretoria in South Africa, said in a statement. “We see the radio equivalent of a laser halfway across the universe.”
Normally, signals from this far away are too weak to be picked up by telescopes like MeerKAT. However, the maser shooting from HATLAS J142935.3–002836 has been further enhanced by a rare phenomenon, called gravitational lensing, first predicted by Albert Einstein‘s theory of relativity in 1905.
Gravitational lensing occurs when electromagnetic radiation from a distant object, such as a galaxy, is bent around a massive object located directly between the source and the observer. It is clear that the radiation does not actually bend (because light always travels in a straight line): instead, it passes through distorted space-time which have been drawn out of form by the enormous gravity of the middle object.
From the observer’s point of view, this phenomenon often creates a halo of light around the central objectknown as an “Einstein ring.” But it also magnifies the light source—or in this case, the microwave source—which makes it a lot easier to analyze the distant object.
The team now plans to point MeerKAT at similar systems in the hope of discovering more secret megamasers or gigamasers lurking in gravitationally lensed objects, which could drastically increase the number of these otherwise rare space lasers they can study.
“This is just the beginning,” Manamela said. “We don’t want to find just one system — we want to find hundreds to thousands.”
