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a cosmic event never seen in 10 years

In 2018, as telescopes around the world scanned the M87 galaxy, 55 million light years away, they captured an event of rare intensity. The supermassive black hole M87* has emitted a gigantic gamma flarean extremely bright and energetic flash of gamma rays, the most powerful form of electromagnetic radiation.

These cosmic events are generally short-lived, but release colossal energy in a matter of seconds that is equivalent to that which our Sun would emit over several billion years.

In the heart of the beast

Let's imagine the supermassive black hole as an immense cosmic whirlpool. Around it gravitates a disk of material, similar to a gigantic ring of gas and dust. This matter, as it falls towards the black hole, heats up considerably under the effect of friction forces – comparable to the phenomenon that warms our hands when we rub them, but on a scale billions of times greater. This intense heat causes the accretion disk to glow, creating the characteristic bright ring seen in the first historic image of M87* (see below).

Years of observations and calculations were necessary to produce this revolutionary image. It shows us the accretion disk of M87* as it appeared on April 10, 2019, a luminous ring of superheated matter orbiting the black hole. © Event Horizon Telescope / Wikipedia

The intense magnetic fields, generated by the rotation of the accretion disk and the black hole itself, play a major role in the formation of relativistic jets, extremely powerful cosmic geysers. These magnetic fields, structured in lines of force, channel part of the superheated material from the disk, accelerating it to speeds close to that of light along the field lines which extend perpendicular to the disk, thus forming two jets plasma collimated.

The Anatomy of a Titanic Eruption

The gamma eruption observed in 2018 represents an event of incredible violence. To understand its magnitude, let's imagine a spatial volume equivalent to 170 times the Earth-Sun distance – a surprisingly compact region on a cosmic scale, just ten times larger than the black hole itself. It was in this relatively small space that the this explosion of phenomenal power.

The mechanism behind this eruption can be compared to a cosmic collision: “lumps” of material, falling into the plasma jet, are violently accelerated. This acceleration is so intense that it generates an immense quantity of gamma rays. The energy released by such an eruption is billions or even trillions of times greater than that of a modern nuclear bomb.

« Intriguingly, the intense variations detected in gamma rays do not appear in other wavelengths, suggesting that the flare area is complexly structured and behaves differently depending on the type of observation. » notes Daniel Mazin, from the University of Tokyo. In other words, the eruption zone behaves like a real chameleonchanging appearance depending on the type of light used to observe it.

A cosmic fundamental physics laboratory

Simultaneous observation of the gamma flare and changes in the bright ring around the black hole provides a unique opportunity to study the laws of physics in extreme conditions. Sera Markoff, from the University of Amsterdam, explains: “ For the first time ever, it is possible to combine direct images of areas near the event horizon with gamma-ray flares from particle acceleration, allowing theories about the origin of these flares to be tested »

By directly observing the interactions between matter and gravity, scientists can therefore verify whether Einstein's predictions are still valid. These cataclysmic events, rare and still partly mysterious, can also be better understood thanks to the combination of direct images and gamma-ray observations. The previously mentioned relativistic jets are extraordinary natural particle accelerators. By studying these phenomena, scientists could discover new acceleration mechanisms, with potential applications in particle physics.

Observations of the M87* explosion greatly deepen our understanding high energy phenomena around supermassive black holes. The analysis of the data collected during this exceptional gamma-ray eruption highlights the richness of the physical processes operating in these regions of space-time where the laws of physics reach their theoretical limits. These will undoubtedly fuel new theoretical models to describe the behavior of matter and energy in these extreme environments and perhaps help us to answer this fundamental question more accurately: where do we come from and where does our Universe come from? ?

  • In 2018, an exceptionally intense gamma-ray flare was observed near the black hole M87*, releasing colossal energy in a compact space.
  • This explosion, caused by the acceleration of particles in plasma jets, is a unique opportunity to study the interactions between matter and gravity.
  • The discoveries around M87* make it possible to test the fundamental laws of physics in extreme conditions.

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