In galaxies, intense streams of high-energy particles arise from the stellar winds of massive stars or the gravitational influence of supermassive black holes, forming what we call galactic winds. In starburst galaxies with rapid star formation, colliding supernova winds create vast bubbles of ultra-energetic particles known as galactic superwinds.
Galaxies vary widely, not just in shape but also in star formation rates. While some produce stars slowly, starburst galaxies forge them at extraordinary speeds.
In these dynamic environments, stellar winds—streams of particles ejected by stars—occur more frequently. When driven by massive stars, spiral density waves, or supermassive black holes, they qualify as galactic winds.
Related topic: Supermassive black holes generate winds that shape all their galaxies
The most intense galactic winds, primarily from supernovae, can collide. A sufficiently strong shock at their interface converts kinetic energy into thermal energy, trapping most of it rather than letting it radiate into space.
This shock creates a dense, scorching-hot gas bubble under immense internal pressure. The bubble expands rapidly, sweeping up surrounding interstellar and intergalactic gases and particles.
Within the bubble, ongoing wind collisions generate further thermal shocks, accelerating its growth. The engulfed intergalactic gas is either shredded by hydrodynamic forces or evaporates via thermal conduction, cooling the medium as the bubble propagates.
These superwinds can span entire galaxies. As established in theoretical models by astrophysicists, they play a crucial role in galactic evolution by expelling vast amounts of material—especially metals—into the halo, enriching the intergalactic medium and fueling future star and planet formation.
