Space is not 100% vacuum, actually. The solar system is in the Milky Way galaxy, and it’s rotating around the center of it and through the various (thin) [gases within the galaxy](https://solarsystem.nasa.gov/internal_resources/125/). In addition, the Sun emits plasma (the solar wind), and stars nearby (Proxima, Alpha Centauri for example) also emit their solar winds, and these winds “clash”.
The [wiki article](https://en.wikipedia.org/wiki/Heliosphere) explains it in detail.
Latest Answers