A unique mixture of radiation from a dead star has been detected in our galaxy, the Milky Way. Indeed, ua dead star located at some 14,350 light years Earth has just become the most important clue to solving the mystery of rapid radio bursts. Earlier this year, the star spat out a colossal burst of milliseconds, and now the very first published analysis of the event notes its similarity to enigmatic extragalactic signals.
First of all, you should know that the rapid radio bursts, or FRB (from English fast radio burst), or Lorimer bursts, are bursts of radio waves lasting a few milliseconds, coming from galaxies located millions of light years from Earth. The first of these was discovered by a team of researchers led by Duncan Lorimer, who analyzed data from an astronomical survey of the Small Magellanic Cloud in 2007. Since then, FRBs have been a mystery to astronomers. During these extremely brief bursts, some FRBs discharge more energy than hundreds of millions of suns (or as much energy as the Sun in 10,000 years).
Since most of the FRBs detected to date are one-off, non-repetitive events that come from far away and cannot be predicted, they have proven to be extremely difficult to locate, and therefore to study. Right now, the explanations offered range from supernovae to extraterrestrials (which remains extremely unlikely), but one type of candidate has shown more and more promise: magnetars.
In the case of the event observed earlier this year, it is the magnetar SGR 1935 + 2154, emitting a burst of radio waves lasting one millisecond, which has been detected by instruments around the world. ” This is the very first observation connection between magnetars and fast radio bursts Said astrophysicist Sandro Mereghetti of the National Institute of Astrophysics in Italy. « This is truly a major discovery, and it helps shed light on the origin of these mysterious phenomena. “, he added.
A magnetar is a type of star with neutrons has an extremely strong magnetic field, which emits high-energy electromagnetic radiation, such as X-rays and gamma rays. For example, in 2004, the explosion of the magnetar SGR 1806-20 was recorded: the energy released affected the upper atmosphere of the Earth when it was 50,000 light years from it ( which means that the explosion took place around 50,000 years ago).
The extremely powerful magnetic fields of magnetars (1000 times more powerful than stars at neutrons medium) have a strange effect. As gravity applies a force inward, keeping the star stable, the magnetic field pulls matter outward, deforming the star.
These two permanent competing forces create a tension that sometimes results in massive starquakes. These are called magnetar explosions and typically produce X and gamma rays. Only very rarely have magnetars been captured emitting radio waves.
Astronomers pay attention to magnetar explosions because we don’t know much about how their magnetic fields work, and any activity we can observe from the phenomenon could help better understand these phenomena. So when the SGR 1935 + 2154 magnetar began to rumble at the end of April, the monitoring instruments around the world were turned in its direction.
Initially, the researchers thought it was a usual magnetar explosion. However, on April 28, an unprecedented event occurred: a very bright radio wave that shockingly resembled a rapid radio burst was detected by several instruments.
This wave was so bright that the telescope of the Canadian Hydrogen Intensity Mapping Experiment, known as CHIME (from the English Canadian Hydrogen Intensity Mapping Experiment), specially designed to detect transient events and responsible for the discovery of a good number of FRBs, could not quite quantify it. And that’s not because the wave was inherently more powerful than the extragalactic FRBs (it was actually inherently weaker), but because it was so much closer.
It is by using data collected by the INTEGRAL satellite of the European Space Agency, that Mereghetti and his team positively associated the signal to the magnetar, analyzed and characterized it. ” Basically, the IBIS imager on Integral allowed us to precisely locate the origin of the wave burst, validating its association with the magnetar Said astrophysicist Volodymyr Savchenko, from the University of Geneva, Switzerland. ” Most of the other satellites involved in the collaborative study of this event were unable to determine its position in the sky – and this was crucial to identify that the broadcast was indeed from SGR 1935 + 2154 “, he added. While the wave itself is a bit weaker than the extragalactic FRBs, almost everything else matches the extragalactic FRB profile.
But there was also another element that surprised scientists: The radio burst had an X-ray counterpart, something scientists had never seen before in an extragalactic FRB. This does not mean that extragalactic FRBs do not have X-ray equivalents: in reality, it could mean the opposite, that the signals are more complex than we previously thought, spitting out several types of radiation below our threshold. detection. ” This is a very intriguing result and it supports the association between the FRBs and the magnetars Mereghetti said. « The FRBs identified so far are extragalactic. They have never been detected with X / gamma rays. An X-ray burst with a luminosity like that of the SGR 1935 + 2154 magetar would be undetectable for an extragalactic source “, he added.
In this case, the counterpart in the x-rays allowed the team to refine the magnetar’s distance measurements. Previously, scientists believed it was around 30,000 light years from Earth. While this is extremely convincing evidence (in favor of the origin of the magnetar for FRBs), however, it would be a mistake to say that all mysteries have been solved. Indeed, according to the researchers, it is quite possible that there are other sources, especially because some of the signals behave very differently.
Indeed, some are stronger, others are weaker. Some others repeat themselves (although most don’t). Two signals were even caught repeating on a cycle. So this is most certainly not the last time we hear about the SGR 1935 + 2154 magnetar.