A strange, repeating signal emanates from the center of the Milky Way

In early 2020, a team of astronomers discoveredan unusual radio signal emanating from somewhere in the center of our galaxy. The signal flashed, appearing and then disappearing, becoming over time 100 times brighter and dimmer. Moreover, the radio waves in the signal had an unusual "circular polarization," which means that the electric field in the radio waves spins in a spiral as the waves travel through space. For the first time, the signal was caught with the Australian Pathfinder telescope, then with the massive ASKAP radio telescope. Other telescopes around the world and in space followed later. But despite all the efforts made, researchers still cannot say with certainty what is the source of the unusual radio waves. It is also interesting that the structure of radio waves does not correspond to anything with which we are currently familiar, so it is likely that a completely new space object could be the source of the signal. But even so, what is it?

Scientists discover more and more unusual signals emanating from the very heart of the Milky Way

Why study radio waves?

Most stars in the observable universeemit light that lies in a certain known range (radio waves, visible light and gamma rays are in the electromagnetic spectrum). For decades, researchers have gazed into the night sky and listened intently to the distant and endless space. Various telescopes have allowed them to observe a wide variety of objects with varying levels of brightness, including, for example, supernovae, pulsars and fast radio bursts.

Fast radio bursts (FRBs) - short but intense pulses of radio waves recorded in the radio range of the electromagnetic spectrum. These impulses last only a few milliseconds and then disappear without a trace.

In general, the center of the Milky Way is a mysterious place.Astronomers believe that there is a supermassive black hole. This region is densely filled with stars, dominated by red giants. But because of the distance and dust between the Earth and the center of the Galaxy, it is impossible to see any object in visible light, ultraviolet light or X-rays.

Some researchers believe there is a mysterious dark matter at the center of the Milky Way

The only thing available to scientists today isradio waves. And some of them are very, very strange and come from the very heart of the Milky Way. Earlier we talked about one of these signals, I recommend reading it.

Interestingly, most of the things thatastronomers see in outer space, are fairly stable and do not change much on the scale of human time. This is why objects that actually change (variables) or appear and disappear (transient) are so interesting. The former are usually associated with some of the most energetic and violent events in the universe, such as the collapse of massive stars. Thousands of transients at optical and X-ray wavelengths have been detected over the past decade.

More on the topic: How do astronomers listen to space?

Mysterious radio signal from the center of the Galaxy

But back to the new signal.According to the authors of a scientific work published in the Astrophysical Journal, they managed to find a temporary source of radio waves in the center of the Galaxy. Researchers at the University of Sydney immediately realized that they were able to register something unusual.

Looking towards the center of the Galaxy, we foundASKAP J173608.2-321635, named after coordinates, said study co-author Professor Tara Murphy. This object is unique in that at first it was invisible, then it became bright, disappeared and reappeared. This behavior is extraordinary and not characteristic of any known cosmic body.

The source of the mysterious radio signal can be identified in the coming decades

But the strangest property of the new signal is that it has very high polarization... This means that the light only fluctuates inone direction, but that direction rotates over time. “The brightness of the object also changes dramatically, 100 times, and the signal turns on and off, seemingly randomly. We have never seen anything like it, ”write the study authors.

Polarized radio sources are extremely rare:we can find fewer than ten circularly polarized sources out of thousands. Almost all of them are sources that we well understand, such as pulsars (rapidly rotating, highly magnetized remnants of exploding stars) or highly magnetized red dwarfs.

But if scientists have no explanation for the strangesignal, what could it be? There are many different types of variable stars and objects in the sky that emit variable light across the entire spectrum. Could it be a low-mass star or a sub-stellar object? Or is it a pulsar? According to astronomers, none of the listed objects match observations.

This image from research showsthe location of the variable source of radio emission and other objects in the center of the galaxy. Yellow outlines indicate ASKAP detection, while blue outlines indicate MeerKAT detection.

As Universe Today writes, astronomers firstsuggested that the source could be a pulsar - a very dense type of rotating dead star - or a type of star that emits powerful solar flares. But the signals from the new source do not match what scientists expect from these types of celestial objects. It is highly polarized like a pulsar, but no pulsations were detected in the collected data.

You will be interested: our radio signals can be heard by the inhabitants of 75 star systems

In search of an unknown object

For nine months of observations, astronomers have foundsix unusual radio signals. But since searches in the visible range of the spectrum did not lead to anything, the researchers decided to search for the object using the Pathfinder radio telescope in Australia, which is located at Parkes Observatory. But again nothing was found.

Not in the least embarrassed, the team carried out the followingobservations with the MeerKAT radio telescope in South Africa, which is even more sensitive. They continued to work to eventually find out if the intermittent signal would appear again.

Fortunately, the signal returned, but we found that the behavior of the source changed dramatically - the source disappeared in one day, although in our previous observations of ASKAP it lasted for weeks, - the astronomers write.

This is a composite infrared image.the galactic center of the Milky Way. It shows new details of complex structures in a hot, ionized gas orbiting a center at a distance of 300 light years.

See also: In search of interstellar monuments or what will remain after us?

Transient detection has become for the teamthe real incentive, however, did not help them determine the nature of the source. But they still managed to find out that the signal was detected only four degrees from the galactic center. Of course, today no one knows what kind of mysterious space object emits such unusual signals, but this ignorance is unlikely to last long.

Over the next decade, a number of newest telescopes will be launched, some of which I covered in more detail in this article.

These tools will enable astronomers to composeincredibly detailed sky maps. It is expected that in the very near future we will find out the answers to the most pressing questions about our space home. So the strange, repetitive and disappearing signal from the heart of the Milky Way will definitely be accurately classified. In the meantime, you can place bets: what do you think this object is? We will wait for the answer here, as well as in the comments to this article.