The Sun is the center of the heliosphere region that extends radially outwards to a termination shock at 75–90 AU, a heliosheath at 80 to 100 AU and then the heliopause at 120 AU. Beyond this is a relatively low density region called the Local Bubble consisting of the local interstellar cloud (which contains the Solar System) and a neighboring G-Cloud complex which contains Alpha Centauri. Less is known about the ISM than the solar wind, but measurements by Voyager 1 and Voyager 2 reported plasma density between 0.001 and 0.005 particles/cm3 at distances of 80 to 120 AU, increasing rapidy beyond 120 AU at heliopause to between 0.05 and 0.2 particles/cm3.[1]
- ^ Gurnett, D. A.; Kurth, W. S. (November 2019). "Plasma densities near and beyond the heliopause from the Voyager 1 and 2 plasma wave instruments". Nature Astronomy. 3 (11): 1024–1028. doi:10.1038/s41550-019-0918-5. ISSN 2397-3366.