Collimated outflows of material ejected during a supernova explosion, shaping the remnant's structure.Supernova jets are narrow, collimated streams of plasma and high-energy particles ejected at near-light speeds during certain types of supernova explosions. Unlike the roughly spherical debris of a typical core-collapse supernova, these jets emerge along the rotation axis of the collapsing star, punching through the stellar envelope and carving out bipolar structures in the surrounding remnant. They are thought to be responsible for the elongated shapes seen in many supernova remnants and for the production of the most energetic cosmic rays.
The idea that supernovae could produce jets dates back to the 1970s, but it gained strong observational support in the 1990s with the discovery of the 'jet supernova' SN 1998bw, which was associated with a gamma-ray burst. Since then, several supernovae with clear jet signatures have been identified, including those with asymmetric remnants like Cassiopeia A.
When a massive star's core collapses, it forms a proto-neutron star or black hole. If the core is rapidly rotating and possesses a strong magnetic field, the infalling matter can be channeled into two opposite directions by magnetic forces, creating a pair of jets. These jets are powered by the rotational energy of the collapsed core, which is extracted via magnetic braking and the winding of field lines. As the jets plow through the stellar material, they heat and accelerate gas, producing intense X-ray and gamma-ray emission, and eventually break out of the star, shaping the supernova remnant into a bipolar or jet-like morphology.
Supernova jets are key to understanding the connection between supernovae and long gamma-ray bursts, and they are invoked to explain the chemical enrichment of the interstellar medium with heavy elements, as well as the acceleration of cosmic rays to energies beyond 10^15 eV.
The jet in the supernova remnant W49B is so asymmetric that it left behind a black hole or neutron star that is now moving at over 1 million kilometers per hour, kicked out of the explosion's center.


















