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13th Oct 2021

Strange radio waves from centre of galaxy are baffling astronomers

Charlie Herbert

Scientist discover weird radio waves coming from the middle of the galaxy

The radio waves could be the sign of a new type of stellar object

An area near the centre of the Milky Way has been emitting weird radio waves that have been baffling scientists.

The waves were discovered by an international team of scientists from Australia, Germany, the US, Canada, South Africa, Spain and France.

The radio waves could suggest a new type of stellar object.

The lead author of the study, which was published in the Astrophysical Journal on Tuesday (October 12), said that the team had “never seen anything like it.”

Ziteng Wang, who is a PhD student in the School of Physics at the University of Sydney, said: “The strangest property of this new signal is that it is has a very high polarisation. This means its light oscillates in only one direction, but that direction rotates with time.

“The brightness of the object also varies dramatically, by a factor of 100, and the signal switches on and off apparently at random. We’ve never seen anything like it.”

According to EurekAlert, many types of stellar body emit variable light across the electromagnetic spectrum, and technological advances are allowing the study of variable or transient objects in radio waves to reveal more secrets of the universe to scientists.

Wang added that whilst the team first thought the source of the radio waves could be a pulsar – a “very dense type of spinning dead star” – the signals don’t match what would be expected from this type of celestial body.

Wang’s PhD supervisor, Professor Tara Murphy, explained that after detecting six radio signals from the source over a period of nine months, the team tried to locate the body in visual light – but they saw nothing.

Prof Murphy said: “We have been surveying the sky with ASKAP to find unusual new objects with a project known as Variables and Slow Transients (VAST), throughout 2020 and 2021.

“Looking towards the centre of the Galaxy, we found ASKAP J173608.2-321635, named after its coordinates. This object was unique in that it started out invisible, became bright, faded away and then reappeared. This behaviour was extraordinary.

“We then tried the more sensitive MeerKAT radio telescope in South Africa. Because the signal was intermittent, we observed it for 15 minutes every few weeks, hoping that we would see it again.

“Luckily, the signal returned, but we found that the behaviour of the source was dramatically different – the source disappeared in a single day, even though it had lasted for weeks in our previous ASKAP observations.”

Astronomers have still not solved the mystery.

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