Stone said: "Well this just contributes to the number of discoveries that Voyager is making and this is one we hoped that we would be able to do and fortunately both Voyagers were working when they reached interstellar space and that was quite an achievement". Until recently, the space surrounding Voyager 2 was filled predominantly with plasma flowing out from our Sun.
One of the big causes for excitement is that an instrument called Plasma Science Experiment, which malfunctioned aboard Voyager 1, is still functional on Voyager 2, which will allow it to send back new data on what it's like in the space between stars. The PLS measurement indicated to Nasa scientists that the probe has certainly left the heliopause.
While both Voyagers have now departed the sun's heliosphere, they are still inside the solar system as it's currently defined.
"It's the same way as a ship cutting through water creates a bow shock wave around it".
During its 41-year journey, Voyager 2 has flown past Jupiter, Saturn, Uranus and Neptune, providing valuable data on all four planets.
Their primary objective was to survey the planets Jupiter, Saturn, Uranus and Neptune - a task they completed in 1989, nearly 30 years ago. Voyager 2 is now operating in temperatures of just about 6.5 degrees Fahrenheit (3.6 degrees Celsius), and for each year that passes the spacecraft can produce 4 watts less of energy. Each alien solar system is nestled in its own equivalent of a heliosphere, pushing out against its own local interstellar space. It was this instrument that observed a "steep decline" in solar wind particle speeds on November 5, this being "the most compelling evidence" of entering interstellar space, according to NASA.
Travelling that far from the centre of the solar... Tradition has it that the edge of the system is beyond the outer edge of the Oort Cloud, which it is estimated to begin at 1,000 astronomical units (AU) from the Sun and to extend to about 100,000 AU. Dodd said that her own goal for the mission is to coax a full 50 years of exploration out of the spacecraft since their launch in 1977. The probes themselves are functionally identical, but Voyager 2 took a more roundabout way to the edge of the solar system.
Together, Voyagers 1 and 2 will provide astronomers on Earth with clues about what lies beyond the heliosphere and what the area outside of the sun's influence might be like. It could also be the true boundary of the solar system, if you consider that to be the point where the sun's gravitational influence drops off.
Mr Nagle said the tracking stations were talking to Voyager 2 for about 15 hours a day.
"The spacecraft no longer has a working recorder on board so it is continuously streaming back that information", Mr. Nagle said.
Mr Nagle said the spacecraft had enough power to run science instruments until 2025. So we really didn't know if Voyager 2 would cross three years ago or three years from now.
"We saw that, in fact, there was no longer any measurable solar wind", Stone said.