An international team of astronomers have for the first time ever discovered unusual signals coming from the direction of the Milky Way’s centre.
The radio waves fit no currently understood pattern of variable radio source and could suggest a new class of planet, said the team from Australia, US, Germany, Canada, South Africa, Spain, and France.
The astronomers first thought it could be a pulsar – a very dense type of spinning dead star – or else a type of star that emits huge solar flares, but the signals did not match these types of celestial objects.
Using the CSIRO’s ASKAP radio telescope, the team found ASKAP J173608.2-321635, and followed-up with the South African Radio Astronomy Observatory’s MeerKAT telescope.
“This object was unique in that it started out invisible, became bright, faded away and then reappeared. This behaviour was extraordinary,” Professor Tara Murphy, from the Sydney Institute for Astronomy and the School of Physics. The findings are published in the Astrophysical Journal.
The team first detected six radio signals from the source over nine months in 2020. The astronomers tried to find the object in visual light, but found nothing. They turned to the Parkes radio telescope and again failed to detect the source.
Because the signal was intermittent, the team observed it for 15 minutes every few weeks, hoping that to see it again. However, this further discovery did not reveal much more about the secrets of this transient radio source.
“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 lead author Ziteng Wang, doctoral 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 added.
While new object, ASKAP J173608.2-321635, does share some properties with Galactic Centre Radio Transients, there are also differences, adding to the mystery. The scientists plan to keep a close eye on the object to look for more clues as to what it might be.