The debate is over. The venerable Voyager 1 spacecraft has entered the uncharted territory of interstellar space.
A team led by Don Gurnett, a space physicist at the University of Iowa in Iowa City, reports compelling evidence that Voyager has exited the heliosphere, the Solar System’s protective bubble of charged particles. ...
... Gurnett and his collaborators calculate that recent increases in electron density found by Voyager 1 match the predicted density of the interstellar medium. The findings, combined with other spacecraft data, indicate that Voyager 1 left the heliosphere on or about 25 August 2012, when the craft was 121 astronomical units (18 billion kilometres) from the Sun.
Gary Zank, a theoretical physicist at the University of Alabama in Huntsville, calls the results definitive. “There is no doubt that we’re in interstellar space,” he says.However, because the craft has not passed through the Oort Cloud, it still technically in the solar system.