Sydney (Australia) Astronomers have picked up unusual radio signals coming from the center of our Milky Way Galaxy. The pattern has been puzzling the researchers and does not match any known astrophysical radio source. An international team led by Ziteng Wang from the University of Sydney has been studying the strange signal and published a report in “The Astrophysical Journal” (DOI: 10.3847 / 1538-4357 / ac2360) in which they note that the signal may originate from a new type of celestial object.
The research team first picked up the signal while scanning the sky with the ASKAP radio telescope in Australia. The signal appeared four times in a row in just a few weeks, said study co-author Tara Murphy of the University of Sydney. Then the signal from the source dubbed ASKAP J173608.2−321635 disappeared, reappearing a couple of times a few months later.
“Sometimes it seems to stay on, detectable for days or weeks at a time, and then other times it can come on and off in a single day, which is extremely fast for an astronomical object,” Professor Murphy said.
There are many types of stellar objects that emit light and other types of electromagnetic radiation, such as radio waves, in various forms. The rotation of the alignment of the signals suggests that the unknown source also rotates around an axis over time.
“At first we thought it could be a pulsar, a very dense and rapidly rotating remnant star core. A star with huge eruptions was also discussed (…) The signals from this new source do not match anything we expect from known stellar objects.” explains Wang.
The object is also very unique because it first appeared almost invisible, then it became lighter and then weakened again, only to reappear. This behavior was observed six times in the course of nine months in 2020. The scientists then tried to locate the source of the radio signals in the visible light spectrum, but had no success. Even with additional help from the Parkes radio telescope, the source could not be found.
When the signal travels through the universe towards us, the detected radio waves are aligned in one direction that rotates. “That rules out almost all astronomical objects we know of,” Professor Murphy said.
Next the team tried their luck with the MeerKAT radio telescope in South Africa. The signal actually returned, but now they found that the behavior of the source had changed dramatically. The source disappeared within a single day, although this process had previously taken several weeks. The new data still did not help to identify the source.
The ASKAP and MeerKAT telescopes are the first parts of the Square Kilometre Array (SKA), the world’s largest radio telescope. It is being planned to be built in Australia and South Africa with receiving stations extending out to a distance of at least 3,000 kilometres. When completed it will have a total collecting area of approximately one square kilometre sometime in the 2020s. The researchers hope that this new system will help them detect the signals source and also more similar objects.