Astronomers Discover a Strange Radio Signal that Repeats Hourly, Cycling Through Three Distinct States.
The signal was first detected in data collected by the ASKAP Radio Telescope in Australia. Named ASKAP J1935+2148, the signal appears to repeat every 53.8 minutes. Regardless of its nature, the signal cycles through three distinct states. At times, it emits bursts lasting 10 to 50 seconds with linear polarization, meaning all radio waves align in the same direction. At other times, its pulses are significantly weaker and exhibit circular polarization, lasting only 370 milliseconds. There are moments when the object goes silent and is lost. Despite several theories about its origin, scientists have yet to explain the signal using current physical knowledge, according to New Atlas. Research on this signal was published in the journal Nature Astronomy on June 5.
The radio signal ASKAP J1935+2148 detected by the ASKAP telescope. (Image: Carl Knox/OzGrav).
“What’s intriguing is how this object exhibits three distinct states, each completely different from one another,” commented Dr. Manisha Caleb, the lead researcher. “The MeerKAT radio telescope in South Africa played a crucial role in distinguishing these states. If the signal did not originate from the same point in the sky, we could not believe that the same object could generate such different signals.”
According to the research team, the most plausible explanation for the strange radio signal is that it originates from a neutron star or a white dwarf. However, the characteristics of the signal do not align with the physical understanding of these two types of objects. Neutron stars and white dwarfs are relatively similar but have some key differences. Both are formed from the deaths of larger stars, and the initial mass of the star determines whether it will become a neutron star or a white dwarf.
Neutron stars regularly emit radio waves and are the primary suspects here. The diverse signals could be generated by interactions between the strong magnetic field of the neutron star and a complex plasma flow. However, a significant problem is that neutron stars always rotate at speeds of just a few seconds per rotation. Physically, such an object cannot rotate slowly enough to take 54 minutes per rotation. In contrast, white dwarfs can rotate slowly like that, but the research team does not know how it could produce radio signals like the ones they detected.
This is not the first time a repeating radio signal from space has surprised scientists. A few years ago, they discovered a signal that transmitted in an 18-minute cycle. The new radio signal has a longer but more complex cycle. Researchers will need to conduct further observations to explain their mysterious origins.
