Surprisingly, we currently live in a region—300 light-years across—called the Local Bubble, which is a vacuum-like domain with very low hydrogen density within the interstellar medium in the Orion Arm of the Milky Way. Only recently –perhaps in the last few million years—did we enter this warm, low-density, partially-ionized region, with its relatively sparse interstellar environment. During this time, the region enclosed by the heliosphere boundary—where the solar wind dominates over the interstellar medium—has been exceptionally large.
