Voyager 1 races toward interstellar space

NPR : Traveling at 636 miles per minute, Voyager 1 is headed toward interstellar space . Right now, the craft is in the outermost layer of the heliosphere, the bubble of charged particles the Sun forms around itself. The solar wind in that area is nil, but the 100-fold greater intensity of high-energy electrons in elsewhere in the galaxy indicates an approaching boundary. Voyager 1 is expected to cross that boundary sometime in the next three years.