We have seen the most powerful microwave laser in the known universe

Astronomers have spotted a laser-like beam of microwaves produced by two colliding galaxies, the brightest and most distant example of this phenomenon ever seen.

To produce a laser, the first atoms must be stimulated into an unstable state with higher energy. Then particles of light, or photons, fired at these atoms will cause them to relax and emit their own photons, causing a chain reaction that produces many more photons in the process. Because each atom emits identical photons, all the light produced has the same frequency, forming a beam of coherent light.

The same process can happen when galaxies merge. Gas from both galaxies is compressed, producing more stars and light. After traveling through dust clouds, this light can excite hydroxyl ions, which are composed of hydrogen and oxygen atoms, to higher energy states. When these excited ions are blasted with radio waves, for example from a supermassive black hole, they can suddenly relax and produce a beam of extremely bright and focused microwave radiation, known as a maser.

Now, Roger Deane at the University of Pretoria in South Africa and his colleagues have spotted the brightest and most distant maser so far, in a galaxy nearly 8 billion light-years away called H1429-0028. The light from this galaxy is distorted by a massive galaxy between it and Earth that acts as a magnifying glass, an effect called gravitational lensing.

Deane and his colleagues used the MeerKAT telescope in South Africa, which consists of 64 linked radio telescopes that act as one giant dish, to look for galaxies rich in molecular hydrogen, which emit light at a revealing frequency. But when they turned MeerKAT toward H1429-0028, they saw light being strongly emitted at a higher frequency, which they knew was only produced by powerful masers.

“We took a quick look at the 1,667 megahertz (frequency), just to see if it was detectable at all, and there was this booming, huge (signal). It was immediately the record,” says Deane. “It was serendipitous.”

The light beam from the galaxy is so bright that the maser can warrant its own category, called a gigamaser, much more powerful than the megamasers observed in galaxies closer to us. “This is about 100,000 times the luminosity of a star, but in a distant galaxy, concentrated into a very, very small part of the (electromagnetic) spectrum,” says Deane.

We should be able to detect similar masers at much greater distances when the Square Kilometer Array in South Africa, a much larger and more sensitive version of MeerKAT, is completed and comes online in the coming years, says Matt Jarvis at the University of Oxford.

Such distant galaxy masses will be from some of the first galaxies to form in the universe and can give us precise information about how galaxies merged far back in time, says Jarvis. “(Masere) needs very precise conditions,” he says. “You need this radio continuum emission, and you need this infrared radiation, which you really only get from dust heating up around and forming stars. To get these very specific physical conditions to get the maser going in the first place, you need intertwined galaxies.”

Astronomy capital of the world: Chile

Experience the astronomical highlights of Chile. Visit some of the world’s most technologically advanced observatories and see stargazing under some of the clearest skies on earth.