A mysterious source of radio signals has been discovered from a region of the Universe where there is nothing

The latest ASKAP radio telescope, which is being built in stages in Australia, has detected a source of radio signals that is strange in all respects, for which there is no explanation yet. The radio pulse arrives at Earth with an interval of 6.5 hours. This is such a long period that it cannot be explained by the current theory of periodic sources such as pulsars, magnetars or white dwarfs. And this secret has yet to be revealed.

An artistic representation of a mysterious radio source. Image source: James Josephides

The source ASKAP J1839-0756 is located in a direction where there are no visible or previously recorded astronomical objects. For example, it could be a white dwarf – the core of a dead and cooling star. With some stretch, this could explain such a long interval between radio pulses, but so far no connection to such objects has been found.

Neutron stars, which are associated with periodic radio signals, rotate very quickly – several times per second. The theory is that they stop emitting radio signals when their rotation speed slows to about one revolution per minute. The radio pulses themselves arise due to the deviation of the axis of the magnetic poles from which the signal originates relative to the neutron star’s rotation axis. Therefore, the magnetic pole rotates and “shines” towards the Earth at a certain time interval. If the magnetic pole is never pointed towards our planet, we cannot detect such a source.

If pulsars are eliminated from the list of suspects, another candidate could be a magnetar. The problem is that magnetars also cannot spin very slowly. In addition, certain conditions must be met for them to emit a radio signal. Astronomers have discovered one magnetar emitting a signal every 6.67 hours, but these are pulses in the X-ray range. No radio signals were detected from it.

Finally, a white dwarf may be the suspected source of the slow radio signal. These objects usually rotate much slower than neutron stars and, in principle, in the presence of strong magnetic fields, can emit radio waves. However, here there must be suitable conditions, for example, it must be a double system.

The discovered slow radio source has another rare feature. Its magnetic pole is oriented almost exactly towards the Earth. This means that radio telescopes register two pulses – one from each of its poles. After the first signal, a slightly weaker second one arrives approximately 3.2 hours later. Only about 3% of all radio sources have been detected in this orientation.

Scientists were definitely lucky with object ASKAP J1839-0756. It can be studied from literally all sides, and its incomprehensible status only fuels interest. Finding the answer to this phenomenon will certainly expand our understanding of the Universe.