Radio waves

Variable signal aligned at the heart of the Milky Way galaxy appeals to scientists – sciencedaily

Astronomers have discovered unusual signals coming from the direction of the center of the Milky Way. The radio waves do not correspond to any currently understood model of a variable radio source and could suggest a new class of stellar objects.

“The strangest property of this new signal is that it has a very high polarization. This means that its light oscillates in only one direction, but that direction rotates over time,” said Ziteng Wang, lead author of the short story. study and doctoral student. at the School of Physics, University of Sydney.

“The object’s brightness also varies considerably, by a factor of 100, and the signal turns on and off seemingly randomly. We’ve never seen anything like it.”

Many types of stars emit variable light across the electromagnetic spectrum. With enormous advances in radio astronomy, the study of variable or transient objects in radio waves is a vast field of study helping us to reveal the secrets of the Universe. Pulsars, supernovae, flaming stars, and rapid radio bursts are all types of astronomical objects that vary in brightness.

“At first we thought it could be a pulsar – a very dense type of spinning dead star – or it could be a type of star that emits huge solar flares. this new source does not match what we expect of recent types of celestial objects, ”Wang said.

The discovery of the object was published today in the Astrophysics Journal.

Mr. Wang and an international team, including scientists from Australia’s national science agency CSIRO, Germany, the United States, Canada, South Africa, Spain and France discovered the object at using CSIRO’s ASKAP radio telescope in Western Australia. Follow-up observations were made with the MeerKAT telescope of the South African Radio Astronomical Observatory.

Mr. Wang’s thesis supervisor is Professor Tara Murphy, also from the Sydney Institute for Astronomy and the School of Physics.

Professor Murphy said, “We have surveyed the skies with ASKAP to find new unusual objects with a project known as Slow Variables and Transients (VAST), throughout 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 out invisible, turned bright, then faded away. reappeared. This behavior was extraordinary. “

After detecting six radio signals from the source over nine months in 2020, astronomers attempted to find the object in visual light. They found nothing.

They turned to Parkes’ radio telescope and again failed to detect the source.

Professor Murphy said: “We then tried out the more sensitive MeerKAT radio telescope in South Africa. As the signal was intermittent, we watched it for 15 minutes every few weeks, hoping to see it again.

“Fortunately the signal returned, but we found that the source’s behavior was drastically different – the source was gone in a single day, even though it had lasted for weeks in our previous ASKAP observations.”

However, this new discovery did not reveal much more about the secrets of this transient radio source.

Mr Wang’s co-director, Professor David Kaplan of the University of Wisconsin-Milwaukee, said: “The information we have has parallels with another emerging class of mysterious objects known as radio transients. from the galactic center, including one nicknamed the “cosmic burper”.

“While our new object, ASKAP J173608.2-321635, shares some properties with GCRTs, there are differences as well. And we don’t really understand those sources, anyway, so that adds to the mystery.”

Scientists plan to keep a close eye on the object for more clues as to what it might be.

“Over the next decade, the Square Kilometer Array (SKA) transcontinental radio telescope will come online. It will be able to create sensitive maps of the sky every day,” said Professor Murphy. “We expect the power of this telescope to help us solve mysteries such as this latest discovery, but it will also open up vast new areas of the cosmos for exploration in the radio spectrum.”

Video showing an artist’s impression of signals from space: