This black hole threw up the remains of its stellar spaghetti three years later

A little AT2018hyz of indigestion several years after filling up?

One of the most striking characteristics of black holes is their propensity to devour any object that passes by. These cosmic monsters are the origin of a gravitational force so intense that nothing can resist them. It doesn’t matter if it’s an entire galaxy or a photon traveling at the speed of light; according to Einstein’s work on relativity, nothing approaching the central zone (the Event Horizon or event horizon) can emerge unscathed.

In most cases, these objects do not consume their prey in one bite. A star can, for example, gradually removed as it passes close to the event horizon; each time it approaches, the black hole tears off a piece of material in the form of long filaments.

A story about”Spaghetti

These events, officially called Tidal Disruption Events (TDE), are the basis of a process with a very explicit name: scientists often talk about ” spaghettification It might sound like a joke, but it is one very serious expression formalized by Stephen Hawking himself in his legendary A brief history of time. Today, the term is regularly used in academic literature.

An artist’s impression of a “spaghettified” star. © ESO, ESA/Hubble, M. Kornmesser

This material” Spaghetti tends to elongate at the periphery of the black hole as it reaches extreme temperatures; they therefore emit a phenomenal amount of radiation. A boon for researchers; this radiation allows them to see them millions of light years away to study this fascinating process. And the study of a very special case that took place recently proves again that there is still a lot to discover about the physiology of black holes.

Exceptional delayed indigestion

While observing AT2018hyz, a black hole located 665 light-years away in 2018, a team of researchers took it by hand in the cake box; he was in the middle of a TDE, enjoying star spaghetti. A rather rare sight, certainly, but already observed by other researchers before. The team therefore deduced that this TDE was “ not particularly remarkable » ; at first sight this observation did not entail revolutionary elements.

But when they looked closer three years later, a big surprise awaited them; AT2018hyz emitted very intense radiation, almost as if it was ” spaghettify ” a star. ” AT2018hyz was radio silent for the first three years, but now it has brightened dramatically to become one of the most intense TDEs ever observed. “, explained Edo Berger, professor at Harvard and co-author of the study.

A detail that left the team confused. Because in general, these radiations tend to appear directly after a TDE, and certainly not years later. However, all readings indicated that the black hole had not absorbed a new star since the 2018 event. It completely surprised us – no one has ever seen anything like it “, explains Yvette Cendes, one of the authors of the study.

A generality or an isolated case?

Neither one nor two, his team therefore submitted special authorization requests with several large telescopes to be able to carry out emergency observations; everyone immediately agreed to shake up their schedules, clearly showing the extraordinary side of this phenomenon.

Well it took them; they were able to confirm that the black hole was indeed ” To throw up material at about half the speed of light. But above all, they were able to confirm that this leftover material actually came from the star that was consumed three years earlier; resounding success. ” This is the first time we have observed such a long delay between the meal and the excursion. says Berger.

And this new observation comes with a whole lot of additional questions that they will now try to answer. They will especially seek to discover how and why did this big baby take so long to burp. They will also check if it is a common process that has gone unnoticed until now or if they have witnessed a rare event.

Answering these questions will help learn more about how black holes feed and grow. And by knowing their importance to the overall dynamics of the universe, this will also make it possible to specify the models that describe the evolution of the cosmos and the objects that exist there.

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