Although astronomers often discover unusual phenomena coming from the galactic core, the Sydney researchers have so far failed to explain their latest discovery.
The radio waves picked up by the Australian SKA Pathfinder (ASKAP) telescope do not appear to fit any known source of radio signals in space.
The researchers are now determined to find out exactly what is happening at the center of the galaxy, which is about 26,000 light-years from Earth.
Ziting Wang, a doctoral student at the University’s College of Physics and lead author of a new study describing this phenomenon, revealed that the signal may indicate the existence of a new class of stellar objects.
He said: “The strangest feature of this new signal is that it has a very high polarization, and this means that its light oscillates in only one direction, but this direction rotates with time.”
“The object’s brightness also varies greatly, by a factor of 100, and the signal is turned on and off seemingly randomly. We’ve never seen anything like it before.”
His discovery was published this week in the peer-reviewed journal Astrophysical.
Stars of all kinds emit light that extends across the electromagnetic spectrum.
The spectrum covers all types of electromagnetic radiation, including visible light, X-rays, ultraviolet radiation, radio waves, and others.
Stellar objects such as pulsars, supernovae, fast radio bursts, and blazing stars have varying brightness.
But so far, none of these things have been able to explain the mystery signal.
“We initially thought it might be a pulsar – a very dense type of rotating dead star – or another type of star that emits massive solar flares,” Wang said. “But the signals from this new source don’t match what we expect from these types of celestial bodies.”
Tara Murphy, Wang’s PhD supervisor, added: “We have been scanning the sky with ASKAP to find new, unusual objects through a project known as Variables and Slow Transients (VAST), throughout 2020 and 2021. Looking at the galactic center, we found ASKAP J173608.2. -321635, according to the name of its coordinates. This thing was unique in that it began invisible, became bright, then faded, and reappeared.”
After the signal was originally detected using ASKAP, the radio waves were confirmed by the MeerKAT telescope of the South African Radio Astronomy Observatory.
In total, the scientists discovered six signals from the mysterious source over a nine-month period in 2020.
“Within the next decade, the Square Kilometer Array (SKA) ICRC radio telescope will come online. It will be able to make sensitive maps of the sky every day,” Murphy said. New vast swaths of the universe to explore in the radio spectrum.