Voyager 1 At the Edge of the Solar System

Via MetaFilter, a really nice if short article from the Houston Chronicle's science blog about Voyager 1's exit or impending exit from the solar system. The test that has been adopted for "leaving the solar system" is evidence of:

1. An increase in high-energy cosmic rays originating from outside our solar system 
2. A drop in charged particles emanating from the sun.
3. A change in the direction of the magnetic field.

At the end of August there was a sharp sustained drop in the charged particles from the sun.  There's some of evidence of the first and third conditions having been met as well, though it's not definitive. "Leaving the solar system," though not sharply defined, is seminal; it will mark Voyager as not just the farthest humans have ever sent a machine, but as the first machine from Earth to travel between the stars. It's taken 35 years to get to our solar system's edge.