Astronomers have discovered a supercharged space laser shooting at Earth from halfway across the universe. The cosmic energy beam, which was partially revealed to us via a weird 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 pair 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 human-made lasers, which work 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 their name. (Laser is an acronym for “light amplification by stimulated emission of radiation”; replace “light” with “microwave” and you get a maser.)
Researchers 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 dubbed “cosmic beacons.”
In a new study, uploaded Feb. 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 dubbed HATLAS J142935.3–002836.
The microwaves shooting out of this system are very stretched, around 18 centimeters in length (7 inches or 1,665 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 was first discovered in 2014 and is around 8 billion light-years from Earth, meaning the microwaves we see were emitted when the universe was about half its current age. This comfortably makes it the most distant megamaser seen to date.
“This system is truly extraordinary,” study first author Thato Manamela, an astronomer at the University of Pretoria in South Africa, said in a statement. “We are seeing the radio equivalent of a laser halfway across the universe.”
Normally, signals from so far away are too faint to be picked up by telescopes like MeerKAT. However, the maser shooting from HATLAS J142935.3–002836 has been further amplified by a rare phenomenon, dubbed gravitational lensing, which was 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 positioned directly between the source and the observer. Obviously, the radiation doesn’t actually bend (because light always travels in a straight line): Instead, it passes through warped space-time that has been pulled out of shape by the immense gravity of the middle object.
From the observer’s point of view, this phenomenon often creates a halo of light around the middle object, known as an “Einstein ring.” But it also magnifies the light source — or in this case, microwave source — making it much easier to analyze the distant object.
The team is now planning to point MeerKAT at similar systems in the hopes of discovering more secret megamasers or gigamasers lurking within 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.”
