NASA's Voyager 1 has crossed a boundary that's one of the last milestones before it departs our solar system. You can listen online to the weird plasma wave sounds of the boundary, called the "solar wind termination shock." It reminds me of glitchy minimalist electronica. University of Iowa physicist Don Gurnett designed the the plasma wave instrument that captured the sound. From a news release:
Kurth compares the termination shock to what happens when water is allowed to run from a kitchen faucet onto the center of a dinner plate. The water — representing the solar wind, a stream of electrically charged particles flowing outward from the sun — strikes the center of the plate and smoothly flows outward in all directions. Somewhere near the edge of the plate, the smooth stream becomes rippled as it runs into slower moving water. This rippled band of turbulence represents the termination shock and the region where it occurs, the heliosheath. Similarly, the solar wind slows from supersonic to subsonic speed as it approaches the gas generated by stars beyond our sun.
Link to news release, Link to "sounds of space" including the termination shock
