On 25th August 2013, according to the news media, "Voyager Probe 'Leaves the Solar System'".  But it seems Astronomers don't all agree about that.

On that date, nearly 36 years after Voyager 1 was launched, the probe crossed the Heliosphere, where the Interstellar Medium (cosmic rays, dust and gas) wins out against the solar wind (plasma blown out by our sun). 

The graph from NASA (right) shows the drop-off of ions from the solar wind in jumps, over a period of a month or so.

However in that case, Voyager 1 must surely have passed the Oort Cloud (understood to be the source of distant asteroids and long period comets)?

Actually no... not even close!  Voyager will not reach the Oort Cloud for another thousand years, and - assuming it travels safely through it - won't exit for around 300,000 years.  By that time it will have already journeyed a quarter of the distance to our nearest stellar neighbour, Proxima Centauri. 

Timeline of Voyager 1's journey

Thanks to our friends in the Sci Show Space YouTube Channel for the graphic and the video below, explaining Voyager 1's journey into inter-stellar space.

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Image Credits: NASA