Mysterious, ‘extraordinary’ radio waves discovered coming from heart of the Milky Way

Mysterious, ‘extraordinary’ radio waves discovered coming from heart of the Milky Way

Mysterious radio waves coming from the heart of the Milky Way have astronomers baffled. At this point, they have no idea what’s causing them, according to a new study published Tuesday in the “Astrophysical Journal.”

A University of Sydney news release said the object was discovered by a team of scientists from across the world, using a telescope in Western Austrialia belonging to the Australian government’s scientific research agency.

The unusual signals coming from the direction of the Milky Way’s center — “radio waves that fit no currently understood pattern of variable radio source” — could suggest a new class of stellar object, the University’s news release 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,” said Ziteng Wang, lead author of the new study and a PhD student in the School of Physics at the University of Sydney.

“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,” Wang said.

Wang explained that at first scientists thought it could be a pulsar – “a very dense type of spinning dead star – or a type of star that emits huge solar flares.” However, signals from the new source don’t match those expected from these types of celestial objects, according to Wang.

The uniqueness of the radio signal — dubbed ASKAP J173608.2-321635 after its coordinates — was that “it started out invisible, then it turned bright and faded away before reappearing again,” which is “extraordinary behaviour,” said Tara Murphy, Wang’s PhD supervisor and a professor at the Sydney Institute for Astronomy and the School of Physics.

Over a nine-month period in 2020, astronomers detected six radio signals from the source, trying to find the object in visual light, but were unsuccessful, the news release said.

Scientists turned to the Parkes radio telescope and again failed to detect the source. However, when using the more sensitive MeerKAT radio telescope in South Africa, Murphy said that, because the signal was intermittent, scientists were able to observe it for 15 minutes every few weeks.

Fortunately, the signal returned, but Murphy noted that the behavior of the source was “dramatically different,” disappearing in a single day, while “it had lasted for weeks” when observed by the Australian telescope.

This further discovery did not reveal much more about the secrets of this transient radio source, and scientists continue to search for answers, according to the University of Sydney news release.