13th October 2021 – (Sydney) Astronomers from Australia’s University of Sydney discovered unusual signals coming from the direction of the Milky Way’s centre.
The discovery, published on Tuesday in the Astrophysical Journal, found the radio waves from an unusual new source, ASKAP J173608.2-321635, named after its coordinates, which could suggest a new class of stellar object.
“The strangest property of this new signal is that it has a very high polarisation. This means its light oscillates in only one direction, but that direction rotates with time,” said Wang Ziteng, lead author of the study and a PhD student in the School of Physics at the university.
“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.”
Many types of star emit variable light across the electromagnetic spectrum. Wang said they thought the object 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 radio waves fit no currently understood pattern of variable radio sources.
However, after surveying the sky to find unusual new objects throughout 2020 and 2021, astronomers did not reveal much more about the secrets of this transient radio source.
Wang’s PhD supervisor Professor Tara Murphy said the behaviour of the object was extraordinary and intermittent, making it harder to reveal the secret of source.
“This object was unique in that it started out invisible, became bright, faded away and then reappeared…We 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 showed up again, but Murphy said the behaviour of the source was dramatically different — the source disappeared in a single day, even though it had lasted for weeks in their previous ASKAP observations.
The astronomers plan to keep a close eye on the object to look for more clues as to what it might be. With tremendous advances in radio astronomy, the study of variable or transient objects in radio waves is a huge field of study helping humans to reveal the secrets of the Universe.