Voyager completed its primary mission in 1980, after taking spectacular photos of Jupiter and Saturn, and has been flying away from the sun ever since. You might recall the many previous times that this farthest-out spacecraft has been suspected of venturing out into the stars, leading many to wonder if NASA is simply crying wolf again. But an analysis of data from the machine's plasma wave sensor suggests that Voyager 1 in fact reached interstellar space more than a year ago, in August 2012.
The unexpected finding relied on the fact that an energetic outburst from the sun, known as a coronal mass ejection, passed by the probe in April, allowing scientists to calibrate their instruments and determine the density of plasma around the spacecraft.
Our solar system is bathed in a constant wind of charged particles and plasma emanating from our central star. This solar wind tapers out at some far distance, many billions of miles beyond Neptune and the rocky belt where Pluto lives, but scientists have always been unsure exactly where. Models of this region of space are notoriously tricky, and new data has often caused researchers to question everything they knew before.
The recent work, published in Science, suggests that Voyager has moved outside the sun's influence and into the plasma of interstellar space, which is cooler and denser than the solar wind. The spacecraft's instruments detected a change in particle density on Aug. 25, 2012 characteristic with the move into interstellar space that has remained the same since.
Voyager 1 will not actually leave the solar system for a very long time. That boundary is thought to extend to a region called the Oort Cloud, a band of icy bodies from which many comets originate. It is hypothesized to exist at a distance 50,000 times that of the Earth and the sun. Of course, Voyager's batteries will run out long before then, probably around 2025, so it won't be sending back any signals after that.
According to wired