Supernovas can become some of the most powerful particle collides in the universe – but only if they pass a lot of gas before exploding, discovers new research.
For almost a century, astronomers detected high energy particles flowing from the distant universe. Known as Cosmic raysThey are mainly made of protons and, sometimes, cores of heavier elements. Most cosmic rays are deflected by the magnetic field of the earth or absorbed in the upper atmosphere, but some do it to the surface. About once every second, a cosmic ray manages to hit your body.
The cosmic rays extend over a wide range of energies, the most powerful exceeding a Peta-Electron Volt (PEV). It is a quadrillion of volt electrons, or up to a thousand times more powerful than the collision energies of the Large collision of HadronsThe most powerful the most powerful atom in the world.
Astronomers suspected for a long time that the explosive death of massive stars can be responsible for these extremely powerful cosmic rays. After all, these supernovas have all the right ingredients: there is a detonation with more than sitting energy, a flood of elementary particles and magnetic fields which can drive these particles in a frenzy before freeing them into the cosmos.
But observations of supernova remains nearby such as Tycho and Cassiopeia has did not meet expectations; The cosmic rays from these places are much lower than expected.
In a newspaper Accepted for publication In the magazine Astronomy & Astrophysics, the researchers saved the supernova hypothesis and found that, in particular cases, the remains of Supernova are indeed capable of becoming “pevatrons”-that is to say explosions capable of generating PEV cosmic rays.
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The team noted that before the outline, a star must lose a large mass – at least two backstage of equipment. This is quite common, because the powerful winds can hunt the outer layers of the atmosphere of a star before the main explosion. But above all, this material cannot be dispersed too largely. He must remain dense, compact and close to the star.
Then, when the supernova finally occurs, the shock wave of the explosive star slams in this material shell. And then all the hell stands out.
While the shock moves through the surrounding shell, the magnetic fields accelerate incredibly powerful energies. These magnetic fields take on random subatomic particles – the debris in the shell – and accelerate them, bouncing them in both directions in the shock wave. With each rebound, the particle earns more energy. Finally, he obtains enough energy to completely leave chaos and flow into the universe.
But in a few months, the system loses steam because the shock wave slows down. It always produces abundant cosmic rays, but not above the Pev threshold.
This scenario explains why we have not directly observed active pevatrons. Even if a supernova is triggered in the Milky Way Every few years, none has been close enough in modern times to observe the short window when they can speed up cosmic rays to these extreme energies. So we should be patient.