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| Cassini at Saturn’s bow shock |
During encounter with an unusually strong blast of solar wind arriving at Saturn, the international Cassini spacecraft detected that particles are being accelerated to ultra-high energies, similar to the acceleration that takes place around supernova explosions.
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| Acceleration around supernova explosions |
Shock waves are commonplace in the Universe, for example in the aftermath of a stellar explosion as debris accelerates outwards in a supernova remnant, or when the flow of particles from the Sun – the solar wind – impinges on the magnetic field of a planet to form a bow shock.
Under certain magnetic field orientations and depending on the strength of the shock, particles can be accelerated to close to the speed of light at these boundaries. Indeed, very strong shocks at young supernova remnants are known to boost electrons to ultra-relativistic energies, and may be the dominant source of cosmic rays, high-energy particles that pervade our Galaxy.
Accelerated electrons at supernova remnant shocks is X-ray emission is reveled by Space telescopes , but these observations are made at great distances and thus the orientation of the local magnetic field can only be poorly measured at best. Without this crucial information, it is difficult to gain a full understanding of the shock acceleration process.