A giant gamma-ray burst reveals its first secrets

On October 9, 2022, astronomers from all walks of life were left in awe by a bewilderingly dense stream of radiation that has since been dubbed BOAT, for The brightest of all time (see our article).

Its origin was quickly associated with the GRB 221009 A event. It is a A gamma ray burst, a cataclysmic explosion that usually accompanies the formation of a black hole. Thus these cues are valuable resources for researchers. In particular, they can extract fascinating information about the life cycle of stars in the early universe. This makes it possible to improve models that describe the global dynamics of the universe.

It is the most powerful type of explosion identified in the universe so far, by far. Specialists estimate that every burst generates The same amount of energy that our good old sun could have produced over 10 billion years! And even in this category, GRB 221009A is an exception.

Naturally, it has been the subject of special interest in the scientific community. Since last October, researchers have been consciously dissecting data collected in the fall of 2022. More recently, a team published new research describing this eruption more precisely.

An exceptionally rare and intense event

Eric Burns, a professor of astrophysics at Louisiana State University, detailed these elements during a symposium reported by NASA teams. And while restraint is generally familiar in science, he didn’t hesitate to heat up the supermachine when describing GRB 221009 A.” It’s a very terrible explosion Breathe accordingly Space.com.

Burns and his team conducted a cross-sectional analysis of about 7,000 gamma-ray bursts detected by the Fermi telescope and the Wind satellite. Then they produced statistical models to estimate the frequency of massive gamma bursts, and the result turned out to be amazing.

” It’s the kind of event that only happens once every 10,000 years. Burns says. ” So there is a reasonable possibility that this is the brightest gamma-ray burst to reach Earth since the beginning of human civilization. “, he thinks.

Beyond timing, the first big question was specification actual severity From the beginning. Indeed, the readings reported by individual instruments did not make it possible to answer this question immediately. And for good reason: This horrific explosion completely saturated the sensors of many observatories and satellites. In other words, they momentarily lost sight of it. So they could not identify all the characteristics of the event.

To achieve this, the researchers crossed the data from the telescope closed and satellites winds with those Jicham C And the’Insight- HXMTIt is a satellite and observatory operated by Chinese teams. This allowed them to determine that GRB 221009A was approx 70 times more powerful than the most powerful cosmic explosion observed so far!

And the least we can say is that they weren’t at the end of their surprises.

Sudden absence of supernovae

For starters, looking at the other events associated with GRB 221009A also note the striking absence of another notable phenomenon.

GRB 221009A belongs to the class of so-called “long” gamma-ray bursts, whose initial emissions last longer than two seconds. Astronomers generally consider the black holes that originated at the origin of these long eruptions to be born out of origin Gravitational collapse of a dying star. As the black hole begins to devour all of the material around it, it releases two jets of highly energetic particles that travel at nearly the speed of light. When they emerge from the star’s corpse, they generate a massive amount of x-rays and gamma rays.

In this scenario, professionals generally expect to see A Supernova – another class of cosmic explosion of catastrophic proportions – a few weeks after the gamma-ray burst. But since recording GRB 221009A, it’s been complete silence; The researchers did not find the slightest trace of it.

So they pulled out all the stops by keeping observation time with two first-order telescopes: Venerable Hubble And the famous James Webb, which has been revolutionizing astrophysics for just over a year. But even these two successful observatories came back empty-handed.

“ We can’t say for sure that there was a supernova, which is pretty amazing given the brightness of the explosion Andrew Levan, professor of astrophysics at Radboud University in the Netherlands, was surprised. “ If there is, it is very secretive he adds.

There are two possible explanations for this phenomenon. The first is that the supernova was obscured by a thick cloud of dust. In this case, James Webb’s new observations might make it more noticeable. High-performance infrared sensors are already able to see through those clumps of material that block the view of standard telescopes. And as a reminder, this has already enabled NASA to directly observe the core of star nurseries that are so important in the global dynamics of the universe.

Another possibility is that there simply was no supernova. ” The entire star could have collapsed directly into a black hole instead of exploding. “Levan says. The team has planned new observations with Hubble and Webb, which they very much hope will allow them to solve this mystery.

Unknown references to the battalion

And that wasn’t the only thing that surprised astronomers. They have also detected elements that they cannot explain at the level of the particle jets described above.

In fact, these planes were particularly narrow and focused, and one of them just happened to be pointing directly at the ground. This made it possible to study them with excellent precision … and to find many discrepancies with existing paradigms.

” Twenty-five years of modeling done well to date fail to fully explain these planes. In particular, we found a file New radio component which we do not fully understand says Kate Alexander, astrophysicist in residence at the University of Arizona.

” This may indicate that additional and as yet unknown structure is present at the core of the jet, and that we may need to revisit models that describe the interaction of black hole jets with their surroundings. specify.

Thanks to the orientation of the plane, it will certainly be possible to observe its remains for many years. So it will be an exceptional opportunity. Astronomers will be able to study the entire life cycle of black hole jets and try to elucidate their role in the dynamics of the universe.

Highlighting the Milky Way

And it’s not over. The signal emitted by GRB 221009A was so intense that it cast doubt on the Milky Way. This allowed astronomers to monitor the remote regions of our galaxy. ” As the first wave of X-rays traveled towards us, some of them were reflected from the layers of dust. This created “light echoes” from the initial explosion in the form Large X-ray rings extending from the epicenter of the explosion NASA press release explains.

These episodes are exceptionally rare. This is only the seventh time in history that astronomers have detected it. GRB 221009A produced 21 in total, three times more than the previous title holder.

Good news for researchers. In fact, the way dust scatters X-rays directly depends on the shape of the grains and their chemical composition. So each circle represents an interesting source of information. We can infer many details about the clouds of matter that fill our galaxy. And this is very important, because this dust is a The basic element in the life cycle of planets and stars.

Study of GRB 221009A has just begun

Finally, studying GRB 221009A was also an opportunity to explore one of the greatest mysteries in astrophysics today. ” We often imagine black holes as entities devouring everything, but do they also return energy to the universe in return? asks Michela Nigro, an astrophysicist at NASA’s prestigious Goddard Center.

They fail to fully answer this burning question. On the other hand, they believe they have found some very promising answers in the data from the European Space Agency’s INTEGRAL Observatory. ” It may be possible to demonstrate that the boat jets were powered by the energy of the magnetic field amplified by the rotation of the black hole explains the press release.

This interpretation would in any case be consistent with other solid models. So it will be necessary to explore this avenue in more depth. If a team comes to a final conclusion, it will be a huge success for all of basic cosmology.

You will understand that the study of GRB 221009A will certainly continue to provide very important information for astronomers in the coming years. It would therefore be advisable to keep an eye on the following publications about this standard gamma-ray burst, as they can greatly improve our understanding of the mechanisms of the universe.

Study text is available here.