"Launched on Sept. 5, 1977 and now more than 11 billion miles from the sun, the Voyager 1 probe was expected to be exiting the solar system by now. But it seems the edge is farther out than scientists thought."
Thought this was just a matter of pure abstract definition? Nope. Unlike country borders, there are a number of layers that can be scientifically defined around the solar system to trace its limits.
Interesting read.