Astronomers have detected a signal that has been travelling towards Earth for over 8 billion years

The discovery was made by the South African MeerKAT radio telescope. And it was made remarkably quickly: it usually takes hundreds of hours of observation to pick up such a distant and rare signal — here, just five were enough. Scientists say this is a dress rehearsal for the era of the new generation of giant telescopes.

Let’s make this clear straight away: ‘space laser’ is a figurative term. We’re not talking about a weapon from science fiction, but a natural phenomenon: clouds of gas in space can amplify and emit radio waves, just as a laser does with light. Such a natural amplifier is called a maser.

Details

To understand why this is important, let’s recall a simple fact: light does not travel instantaneously. Scientists themselves compare this to a letter sent by post. If a friend sends you a letter from abroad, by the time you read it, the news in it is already out of date. In space, light plays the role of the letter. ‘News’ from this galaxy has taken 8 billion years to reach us — which means we see it not as it is now, but as it was in the distant past.

How far back? The universe came into being around 13.8 billion years ago. So we are looking at it at an age when it was less than half its current age — a ‘baby’, as astronomers put it. In that era, galaxies were far more ‘turbulent’: they collided more frequently, formed stars more actively, and bore no resemblance to the calm, mature galaxies in our neighbourhood today.

The signal detected is a megamaser, that is, a maser of incredible power. A standard cosmic maser is already impressive, but a megamaser is a million times brighter. (There are even more powerful ones — gigamasers, a billion times brighter than a standard maser.) Such objects are extremely rare, and detecting one so far away was previously almost impossible.

Two factors helped us act so quickly. The first is gravitational lensing. A massive object, another galaxy, happened to lie between us and the distant galaxy; its gravitational pull acted as a natural lens and amplified the incoming signal. The second was the telescope itself. MeerKAT covers a wide range of radio frequencies, and whilst astronomers were searching the data for neutral hydrogen, a signal from a megamaser was unexpectedly discovered in the same recording.

Why this is important

Scientists readily admit that a single observation does not usually change our understanding of the Universe — large samples of objects are needed to draw serious conclusions. But what was impressive here was the combination of record-breaking distance and the speed of the discovery.

The main significance of the discovery is that it proves: technology finally allows us to detect very faint signals from the distant past. This signal is millions of times weaker than a mobile phone signal, and to isolate it, supercomputers were required to perform trillions of calculations over several days in a row — literally ‘filtering out’ the useful signal from the noise.

And if such a signal can be detected in five hours, it means that future sky surveys will be able to find similar objects on a massive scale. And this paves the way for major scientific discoveries. Megamasers usually form where galaxies collide, and at the centre of almost every large galaxy sits a supermassive black hole. When galaxies merge, their black holes gradually spiral towards each other — and in the end are capable of generating gravitational waves, that is, ripples in space-time itself.

By identifying such systems, astronomers are catching galaxies at a crucial stage in their lives — in the ‘countdown’ before the collision. Let us emphasise: the actual merger of black holes and the burst of gravitational waves have not yet been observed here — this is an expected scenario that next-generation detectors will be able to verify.

Background

Radio astronomy studies the Universe not in visible light, but in radio waves — this allows us to peer into places ordinary telescopes cannot reach, including through clouds of gas and dust. Every atom and molecule emits radiation at its own characteristic frequencies, and scientists use these ‘chemical fingerprints’ (spectral lines) to determine the composition of distant gas.

MeerKAT, located in South Africa, is today considered one of the world’s best radio telescopes. But this is merely a precursor to a far more ambitious project — the SKA (Square Kilometre Array) observatory, a unique international ‘mega-telescope’. At the same time, another next-generation instrument is being designed in the US — the ngVLA, which operates at higher frequencies. Together, they will form the twin pillars of future radio astronomy.

The discovery itself is also a story about South Africa’s scientific standing. To pick up a signal from such a distance, one needs not only sensitive antennas, but also powerful computing platforms and experts capable of working with massive data sets. The country has both — which means South Africa is cementing its role as one of the world’s centres for ‘data-intensive’ astronomy.

Source

The research was carried out using the MeerKAT radio telescope (South Africa). The authors — Thato Manamela, a postdoctoral researcher at the University of Pretoria, and Roger Dean, director of the Inter-University Institute for Data-Intensive Astronomy (IDIA) and a professor at the universities of Cape Town and Pretoria.