Friday , January 28 2022

Strange radio waves from the heart of the Milky Way



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Strange radio waves displayed as spirals reaching the Earth from a distant point of light in space.
An artistic representation of the strange radio waves coming from the heart of the Milky Way. These are not similar to previously detected radio signals and are puzzling scientists about their origin. The source is called ASKAP J173608.2-321635, based on its coordinates in the sky. Image by Sebastian Zantilomo / University of Sydney.

Strange radio waves from an unknown source

Radio emissions are common in the universe. They are created by everything from planets and stars – exotic objects like pulsars and black holes – galaxies – and of course human technology. This week (October 12, 2021) astronomers said they detected new and unusual radio wave signals, unlike those found in the past. The radio waves are coming from the center of our Milky Way galaxy. And so far, scientists have not explained them.

Astronomers have discovered the changing signals using the ASKAP radio telescope in Australia. Radio emission behavior does not match the pattern of a known source of radio signals. It could be that a New A type of stellar object, the scientists said.

Zitang Wang at the University of Sydney School of Physics led the team of international astronomers from Australia, Germany, the United States, Canada, South Africa, Spain and France who saw the signals. They published their article reviewed by the intriguing ages in The Astrophysical Journal On October 12th.

Variable signal with unknown pattern

The source of the signals is called ASKAP J173608.2-321635, but astronomers do not know what the source actually is. It is located toward the center of our Milky Way galaxy. Wang said:

The brightness of the object […] Changes dramatically, by a factor of 100, and the signal turns on and off probably randomly. We have never seen anything like it.

Whatever it is, it’s very polarized and swaying, as Wang explained:

The strangest feature of this new signal is that it has a very high polarization. This means that its light oscillates in only one direction, but this direction rotates over time.

See animated representation of the radio signals in the video below:

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Invisible to the visible and back

One of the most unusual things originally is the way it is. Terra Murphy of the Institute of Astronomy in Sydney and the School of Physics said:

We surveyed the sky with ASKAP to find new and unusual objects with a project known as Slow Variables and Transient (VAST), during 2020 and 2021. Looking towards the center of the galaxy we found ASKAP J173608.2-321635, named after its coordinates. This object was unique in that it started invisible, became bright, faded and then reappeared. This behavior was unusual.

Astronomers have identified six signals over a nine-month period in 2020. However, when astronomers tried to find the source in visual light, using optical telescopes, they saw nothing. The Parks Radio Telescope in Australia has also gone up.

But then, the MeerKAT radio telescope in South Africa, a more sensitive array of telescopes than Parks, Made Identify him. The signal was there, though alternately and different. Murphy described the signal:

Fortunately, the signal came back, but we found that the original behavior changed dramatically. The source disappeared in one day, although it lasted for weeks in our previous observations on ASKAP.

A man with dark hair stands in front of an arched opening in a brick wall.
Zitang Wang, of the School of Physics at the University of Sydney in Australia, led the research team that discovered the strange radio signals. Image via University of Sydney.

What could be the source of the strange radio waves?

Wang and his team ruled out that it may be a pulsar, a fast-moving neutron star that emits lighthouse-like energy beams:

At first we thought it might be a pulsar – a very dense type of rotating dead star – or another type of star that emits huge solar flares. But the signals from this new source do not match what we expect from these types of celestial beings.

The signals also appear to be different from those generated by objects such as supernovae, flaming stars and fast-moving radio bursts (FRBs). These objects also change, but sorry, there is no match for the recently discovered oddities.

However, there seem to be some similarities with other mysterious sources near the so-called galactic center Temporary Radio Galactic Center (GCRT). David Kaplan of the University of Wisconsin-Milwaukee explained:

The information we have has several parallels to another emerging class of mysterious objects known as galactic center radio transmitters, including one dubbed the “Cosmic Box.”

While our new object, ASKAP J173608.2-321635, does share certain assets with GCRTs, there are also differences. And we don’t really understand these sources anyway, so that adds to the mystery.

A bright white spot is surrounded by glowing cloud-like features, with the arrow pointing to one of them.
GCRT J1745-3009 is a galactic central radio transient (GCRT) in the central region of the Milky Way. The GCRT has some similarities with the ASKAP J173608.2-321635 object, but there are also differences. Image via the NRL / SBC Radio Group Galaxy / Wikipedia.

Next steps

The discovery is a puzzling mystery to scientists, and naturally they want to understand it. So what comes next? Investigators plan to continue to monitor the signals as much as possible. In addition, they will get help with this task, thanks to the construction of a new powerful radio telescope. According to Murphy:

In the next decade, the Transcontinental Radio Telescope (Kilometer Array Array (SKA)) will go online. He will be able to create sensitive maps of the sky daily. We expect the power of this telescope to help us solve mysteries such as this latest discovery, but it will also open up many new parts of the cosmos for exploration on the radio spectrum.

Meanwhile, scientists will continue to listen to current telescopes, hoping to find more clues. Whatever this riddle turns out to be, it will provide new and exciting insights into our universe.

Bottom line: An international team of astronomers has identified strange radio waves coming from the heart of the Milky Way. They are not similar to those found earlier, and they may result from a new type of cosmic object.

Source: ASKAP J173608.2–321635 discovery as a very polarized transient point source with the Australian Pathfinder SKA

Source (pre-print): ASKAP J173608.2-321635 discovery as a very polarized transient point source with the Australian SKA Pathfinder

Via the University of Sydney

Through the University of Wisconsin-Milwaukee

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