They detect, for the first time, a radio signal sent by a two -star system

For about a decade, a new cosmic phenomenon has been baffling the radioastronomes around the world: strange radio pulses, from inside our own dairy road and last for several seconds to whole minutes. Emissions, therefore, very different from those of the pulsares, stars of highly magnetized neutrons that turn very quickly and whose radio pulses barely last milliseconds.

Called ‘long -term transitory’ (LPT) these mysterious signals are also repeated in time scales ranging from ten seconds to minutes or even hours, something that no known pulsar is capable of doing.

With hardly any evidence about the possible origin of these mysterious signals, researchers have already formulated different hypotheses in this regard, but none of them has been proven. And now, an international team of astronomers led by Iris de Ruiter, from the Australian University of Sidney, has managed, for the first time, to demonstrate that a ‘strange couple’ of stars, formed by a white dwarf and a red dwarf that orbit each other every two hours, are throwing these long radio pulses into space.

Mysterious signals

The study, just published in ‘Nature Astronomy‘, focused on a collection of these mysterious periodic radio signs detected in 2022 by Ruiter’s own, which at the time of conducting the study was at the University of Amsterdam. The researcher, together with the physicist of the University of Oxford Kaustubh Rajwade and using a novel image technique developed by themselves, managed to find several LPT in the data of the Low Frequency Array International Telescope.

Thanks to the new method, of Ruiter and Rajwade, they detected up to seven pulses from a single source, which they designated as ILTJ1101, a bright point located 1,600 light years away in the direction of the constellation of the Major Osa. As if it were a flash of light, but in the wavelength of the radio, each pulse lasted several seconds to whole minutes and, strangely, everything was repeated at regular intervals, such as a cosmic clock that marked once every two hours.

«These radio pulses – explains Charles Kilpatrick, co -author of the study – are very similar to the FRB (Fast Radio Burst, or rapid radio bursts), but each one has different lengths. In addition, they have much lower energies than the FRB and generally last several seconds, instead of milliseconds. And we still do not know if there is a continuum between long -term radio transitory and FRB, or if they are different populations ».

Not a star, but two

Immediately, Kilpatrick accessed other great telescopes to confirm the observations, and discovered that it was not a star, but two, and that together they were generating the mysterious sign. The two stars, a white dwarf and a red dwarf, orbit around a common center of gravity once every 125 minutes, just the interval that existed between the pulses. And their orbits are so tight that their magnetic fields overlap, likely cause of the mysterious radio emission pulses every two hours.

A white dwarf is a stellar ‘corpse’, what remains when a low or intermediate mass star, like our sun, exhausts its nuclear fuel and violently expels its outer layers, leaving behind an extremely dense and hot extremely, the size of the earth, but with almost the entire original mass of the star. Red dwarfs, however, are the most common type of star in the universe. They are much smaller and cold stars than our sun, and also much less bright. Instead, they have an extremely long life.

According to the researchers, the unusually long radio pulses could arise from the strong magnetic field of the white dwarf, but they could also be the result of the interaction of the magnetic fields of both stars. However, more observations will be needed to clarify it.

«It was especially great to add new pieces to the puzzle we work with experts from all kinds of astronomical disciplines – says De Ruiter. With different techniques and observations, we approached every time a little more to the solution, step by step ».

Thanks to this discovery, astronomers now know that neutron stars do not have the monopoly of radio pulses. In recent years, other research groups had already discovered a dozen radio emitters of this type. But none of them has yet managed to accurately identify the source from which they come.