Key Findings
- An enigmatic radio signal repeating every hour in three distinct modes.
- No known physical explanation matches its characteristics.
Discovery
Astronomers have detected an unusual radio signal, named ASKAP J1935+2148, using the ASKAP radio telescope in Australia. The signal appears in three distinct states in a repeating cycle of 53.8 minutes. In one mode, it emits bright bursts lasting 10-50 seconds with linear polarization, indicating aligned radio waves. In another, it exhibits weaker pulses with circular polarization for just 370 milliseconds. At times, the object becomes invisible, emitting no signal.
Origin Unclear
Scientists have proposed possible sources for the signal, but none fully explain its behavior based on current physical knowledge, according to New Atlas. The findings were published in the journal Nature Astronomy on June 5.
Possible Sources
"The exciting thing is that this object changes its behaviour dramatically between these three different modes," said Dr. Manisha Caleb, lead author of the study. "The MeerKAT radio telescope in South Africa was crucial in helping us distinguish the different modes. If the signal was not coming from the same point in the sky, we wouldn't believe it was the same object making all these different signals."
Neutron stars or white dwarfs are the most likely sources of the strange radio signal, according to the research team. However, the signal's characteristics do not match known physics for either of these types of objects.
Magnetic Interaction Hypothesis
Neutron stars and white dwarfs are quite similar, but with key differences. Both form from the deaths of massive stars, with the initial mass of the star determining whether it becomes a neutron star or a white dwarf.
Neutron stars are known to emit radio waves and are prime suspects for this signal. The varying signal might be caused by interactions between the neutron star's strong magnetic field and a complex plasma environment. However, a major issue is that neutron stars spin very rapidly, completing one rotation in just a few seconds. Physics dictates that such an object cannot rotate as slowly as 54 minutes per cycle.
Slow-Rotating White Dwarfs
White dwarfs, on the other hand, can rotate slowly enough, but the research team is unsure how they could generate a radio signal like the one detected.
Previous Enigmatic Signals
This is not the first time scientists have detected puzzling repeating radio signals from space. Several years ago, an 18-minute repeating signal was found. The new radio signal has a longer period but is more complex. Further observations are needed to unravel their mysterious origins.