E. Edge of the Heliosphere
Discovery of a Hydrogen Wall
The partially ionized LISM and the solar wind are separated
  by a complex set of plasma and neutral atom boundaries of
  enormous scale, located between ~90 and ~250 AU from the sun.
The first of these boundaries, the HYDROGEN WALL, a wall of
  interstellar neutral hydrogen slightly more than twice the interstellar
  density and some 100 AU wide, has been detected. Offered the first
  glimpse into the global structure of the 3D heliosphere.

HOW: The detection of the hydrogen wall resulted from the
serendipitous convergence of predictive theoretical modeling,
observations that tried to place limits on the D/H ratio, and a
multi-disciplinary approach