NASA - Voyager Enters Solar System's Final Frontier

NASA - Voyager Enters Solar System's Final Frontier: "'The consensus of the team now is that Voyager 1, at 8.7 billion miles from the Sun, has at last entered the heliosheath, the region beyond the termination shock,' said Dr. John Richardson from MIT, Principal Investigator of the Voyager plasma science investigation.

The termination shock is where the solar wind, a thin stream of electrically charged gas blowing continuously outward from the Sun, is slowed by pressure from gas between the stars. At the termination shock, the solar wind slows abruptly from its average speed of 300 to 700 km per second (700,000 - 1,500,000 miles per hour) and becomes denser and hotter. "