Scientists in Australia have identified an unusual radio signal emanating from space. This peculiar signal flashes for nearly an hour, the longest duration ever observed. Multiple observations revealed that the signal emits long, bright flashes of weak but rapid pulses, and at times, it emits nothing. Scientists have yet to determine an explanation for this unexpected phenomenon.
The newly discovered radio signal exhibited an hour-long cycle, making it a rare occurrence
Detecting radio signals from beyond our planet is not uncommon, as astronomers frequently observe numerous radio wave bursts originating from across the universe, known as radio transients. These radio transients occur sporadically throughout the universe, some following patterns and others flickering only once. According to researchers, most radio transients originate from rotating neutron stars called pulsars. These stars emit regular bursts of radio waves, akin to cosmic lighthouses. Typically, these neutron stars rotate at astonishing speeds, completing each rotation in mere seconds or fractions of a second. However, the newly discovered radio signal (or transient) exhibited an hour-long cycle, making it a rare occurrence.
Researchers at Wajarri Yamaji Country in Western Australia have named the new periodic radio transient ASKAP J1935+2148. The numbers in the name indicate the location of the radio signal in the sky, detected using the CSIRO’s ASKAP radio telescope. While using ASKAP, the team monitored a gamma-ray source and searched for pulses from a fast radio burst when they identified ASKAP J1935+2148. The signal stood out due to its “circularly polarised” radio waves, meaning the direction of the waves corkscrews around as the signal travels through space.
Further observations revealed that ASKAP J1935+2148 belongs to a relatively new class of long-period radio transients. Only two others have been discovered, and ASKAP J1935+2148’s 53.8-minute period is the longest so far. The origin of the signal, with such a lengthy period of appearance, remains a significant mystery, according to the team. One potential explanation is that it is a slow-spinning neutron star. However, the possibility of the object being a white dwarf cannot be dismissed. A white dwarf is an Earth-sized remnant of a burnt-out star that has depleted its fuel.
White dwarfs often have slow rotation periods, but the team is unaware of anyway one could generate radio signals of this intensity. Additionally, there are no other highly magnetic white dwarfs nearby, making the neutron star explanation more likely. One hypothesis is that the object is part of a binary system in which a neutron star or white dwarf orbits another unseen star. “Further research is needed to confirm what the object is, but either scenario would provide valuable insights into the physics of these extreme objects”, the team wrote in their research paper. The research was published in Nature Astronomy.