We are on our way to our neighboring galaxy, the Andromeda Nebula. After 1'000'000 light years, we have almost half the distance (just 2.25 million LY) completed. Since leaving our galaxy for approximately 100'000 LY we have passed no star more. The space between the galaxies is nearly empty. There are about 4 H-particles per cubic meter.
This radioactivity is comparable to the overall Swiss inventory of all reactors, including the waste produced over the entire operating time.