Voyager 1’s interstellar entry reveals a porous, imperfect solar boundary

Voyager 1 crossed the heliopause into interstellar space in 2012–2013, but the boundary proved porous and layered rather than a clean edge, with a sharp drop in inner solar-wind particles while galactic cosmic rays rose and the magnetic field did not rotate as expected. The crossing was confirmed by plasma-density oscillations from a March 2012 coronal mass ejection, and Voyager 2 later crossed the boundary in a different region with similar results. The inner region remains poorly understood, and both spacecraft—now low on power—continue to return data as they drift through the outer reaches of the solar system.