Scientists have detected radio signals close to the center of the galaxy called ASKAP J173608.2-321635, but they have not been able to tell which type of cosmic object would best suit its peculiar properties.
“ASKAP J173608.2-321635 may represent part of a new class of objects being discovered through radioimaging surveys,” explained the team of astronomers led by Ziting Wang of the University of Sydney, Australia.
ASKAP J173608.2-32163 was discovered using the Australian Pathfinder Square Kilometer Array (ASKAP), one of the most sensitive radio telescopes ever built, designed to delve deeper into the radio universe.
Indeed, the telescope has proven adept at finding things we haven’t seen before, such as individual radio circuits (which are not yet known), undiscovered galaxies, and mysterious fast radio bursts.
ASKAP J173608.2-32163 may turn out to be a known type of cosmic object, but if that happens, it could end up extending the definition of any object.
Scientists note that it is highly variable, emitting radio waves for weeks at a time, and then disappearing on rapid timescales. The signal is also highly polarized, that is, the direction of oscillation of the electromagnetic wave is twisted, linear and circular.
Scientists say that ASKAP J173608.2-32163 is also a “deceptive beast”, and whatever this object may have been, it had not been seen before ASKAP’s discoveries, which were made during an experimental survey of the sky for transient radio sources. Between April 2019 and August 2020, the signal appeared in the data 13 times.
Follow-up observations in April and July of 2020, using a different radio telescope, Murriyang in Parks, Australia, yielded nothing.
But the MeerKAT radio telescope in South Africa was able to pick up the signals, in February 2021. The Australian Integrated Telescope Consortium (ATCA) also made the detection in April 2021.
This supports and validates ASKAP’s detections, but it also indicates that the source is quite elusive, as the source has not appeared in X-ray and near-infrared observations, nor in archives of radio data collected by multiple instruments examined by astronomers.
Polarization refers to scattering and magnetism, possibly in part due to dust and magnetic fields in the interstellar medium between us and the source, although the source itself could also be highly magnetised.
The source of the newly discovered radio signals is incompatible with pulsars, and X-ray binaries, gamma-ray bursts and supernovae have also been excluded.
However, the object does share some characteristics with a type of mysterious signal that has been spotted near the galactic center, known as GCRTs, three of which were identified in the 2000s, and more are awaiting confirmation.
These sources are not yet fully explained, but they have many features in common with ASKAP J173608.2-32163.
And if ASKAP J173608.2-32163 is a GCRT, then ASKAP discovery can help us find more of these sources, and what they are.
Source: Science Alert
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