Chinese students discover strange radio waves in space

Are spiral radio waves from space signals sent to us by aliens?

Distant points of light in space send strange spirals of radio waves to Earth

An artist's graphic representation of a spiral radio signal. The signals were unlike any previously detected radio signals, and scientists were baffled by their origin. It was named ASKAP J173608.2-321635 based on the coordinates of the radioactive source in space. Photograph: Sebastian Zettilomo/University of Sydney

Strange radio waves of unknown origin

The emission of radio is common in the universe. Objects that emit radio include planets, stars, galaxies, exotic objects like pulsars and black holes, and of course all kinds of human technology. On October 12, 2021, astronomers said they had detected a new unusual radio wave signal that was unlike anything seen before. The radio waves come from the direction of the center of our Milky Way galaxy. So far, scientists have no way to explain them.

Astronomers found the variable signals using the ASKAP radio telescope in Australia. The pattern of the radio transmissions does not match any known radio source. Scientists speculate that this could be a new class of stars.

The signals were observed by an international team of astronomers from Australia, Germany, the United States, Canada, South Africa, Spain and France, led by Ziteng Wang of the University of Sydney's School of Physics. They published their intriguing findings in a peer-reviewed paper in the Astrophysical Journal on October 12th.

Variable signal of unknown mode

The source of the signal is called ASKAP J173608.2-321635, but astronomers don't know exactly where it came from, just in the direction of the Milky Way's center. "The brightness of objects varies greatly, by a hundred times, and the signal appears and disappears apparently at random," Wang said. We've never had anything like this."

Whatever it is, high polarization and high oscillations are the most obvious features of this signal, as Wang explained: "The strangest property of this new signal is that it has a very high polarization. That means its light oscillates in only one direction, but that direction rotates with time."

Never see, never see, and so on

One of the most extraordinary things about this source is how it was discovered. Tara Murphy, of the Institute of Astronomy and the School of Physics in Sydney, said: "From 2020 to 2021, in the so-called VAST research project, we have been scanning the sky with the radio telescope ASKAP in the hope of finding unusual new objects. Looking toward the center of the Milky Way, we spotted ASKAP J173608.2-321635, named after its coordinates. This is made up of the telescope that found it and its coordinates in the sky." What makes this object unique is its unusual pattern of appearance: it disappears at first, becomes increasingly bright, then fades out again, and finally reappears."

In 2020, astronomers detected six signals over a nine-month period. But when astronomers tried to look for visible sources with optical telescopes, they couldn't see anything. The Parkes Radio Telescope in Australia is also empty.

But then the MeerKAT Radio Telescope in South Africa, a group of telescopes even more sensitive than Parks, did detect it. The signal was there, albeit on and off, and varied.

Murphy described the signal this way: "Fortunately, the signal came back, but we found that the source was behaving very differently than before. While in our previous ASKAP observations, the radiation source lasted for weeks, this time it disappeared within a day."

The dark-haired man stood in the arched doorway of the brick wall

The strange radio signals were discovered by a team of researchers led by Ziteng Wang of the School of Physics at the University of Sydney in Australia. Photo credit: University of Sydney

What is the source of the strange radio waves?

Wang and his team ruled out the possibility that it was a pulsar. A pulsar is a rapidly spinning neutron star that emits a beam of energy like a lighthouse. "At first we thought it might be a pulsar -- a spinning dead star that emits intense energy -- or a star that explodes huge flares," they said. However, the signal produced by this new source does not match our expectations for these types of objects."

The signals also appear to be different from those produced by celestial bodies such as supernovae, flaring stars and fast radio bursts (FRBS). The electromagnetic waves they emit are also variable, but unfortunately they don't match the strange new signals.

However, it does seem to share some similarities with the other mysterious source of signals near the Milky Way's center, the Galactic Central Radio Transient Source (GCRT). David Kaplan of the University of Wisconsin-Milwaukee explains: "The information we are receiving has some similarities to another emerging class of mysterious objects called Galactic central radio transient sources. The GCRT also includes a body known as the Cosmic Burp.

Our new target, ASKAP J173608.2-321635, does have some properties in common with GCRT, but there are also many differences. And because we don't really know the sources of these signals, our confusion continues to grow."

The bright white blob, as shown by the arrows, is surrounded by a dim, glowing cloud

GCRT J1745-3009 is a Galactic Central Radio Transient Source (GCRT) in the Galactic central region. GCRT shares some similarities with celestial body ASKAP J173608.2-321635, but there are also differences. Photograph: NRL/SBC Galaxy Centre Broadcast Group/Wikimedia Commons

The next step

For scientists, the discovery was puzzling, and of course they wanted to understand it. So what's next? The researchers plan to continue monitoring as many signals as possible. And their mission will get a boost thanks to a powerful new radio telescope being built.

Within the next decade, according to Murphy, the transcontinental Square Kilometre Array (SKA) radio telescope will be online. It will be able to take high-resolution images of space every day. With the power of this telescope, we will hopefully be able to solve mysteries like this latest discovery, and it will open up vast new areas of exploration of the radio spectrum of the universe.