The Structure of the Warm Local Interstellar Medium. The Science Fictional Setting Slower than Light - a novel in progress Ten thousand years in the future, humans have colonized over a hundred planets, using relativistic ramships to travel at near the speed of light from star system to star system.
Humans colonize marginally inhabitable worlds, deserts and ice planets.
A plucky crew of humans mount an expedition to try to beat their delphine competitors to this prize. Some grains of dust have an unusual pattern of iron inclusions whose x-ray diffraction yield a fragment of the message, which must then be pieced together. This is analogous to how we decode DNA, by breaking into smaller fragments and reading each fragment. So the message is all around us, floating in space for three million years, waiting to be found. I need the density of stars, and most important density of G-class stars, in the solar neighborhood.