An unusual signal has been detected coming from center of the Milky Way - or that direction. The findings have been reported in The Astrophysical Journal. The pattern of radio waves does not fit with anything people are currently familiar with, so it may be some new type of stellar object. Radio waves, visible light, and gamma rays, for some examples, are all in the electromagnetic spectrum, and most stars emit light in that fits somewhere in that spectrum. Different telescopes have allowed scientists to observe various objects in the Universe that have variable brightness levels, including supernova, pulsars, and fast radio bursts, for example. But this newly detected object is unusual.
"At first we 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 from this new source don't match what we expect from these types of celestial objects," said lead study author Ziteng Wang, a graduate student in the School of Physics at the University of Sydney.
"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."
An international team of researchers performed this work, which relied on the ASKAP radio telescope of Australia's national science agency CSIRO, and additional data from the MeerKAT telescope at the South African Radio Astronomy Observatory. The ASKAP J173608.2-321635 object, named for its coordinates, was invisible at first, then became bright. It faded after that and then reappeared.
"This behavior was extraordinary," said study co-author Professor Tara Murphy of the Sydney Institute for Astronomy and the School of Physics.
It took time and effort to see the object again, and it was finally revealed with MeerKAT.
"Luckily, the signal returned, but we found that the behavior 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," said Murphy.
The researchers plan to continue to make observations to learn more about this object, and new technology is set to come online in the future, including the transcontinental Square Kilometre Array (SKA) radio telescope, which may help them solve the mystery.