The voyager probes, launched in 1977, have already travelled nearly 17.7 billon kilometers (or 11 billion miles) into our solar system. NASA project scientists believe that it’s about to become the second man made object to leave the heliosphere and reach interstellar space. Voyager 1, it’s counterpart, was the first object to reach interstellar space.
“We’re seeing a change in the environment around Voyager 2, there’s no doubt about that. We’re going to learn a lot in the coming months, but we still don’t know when we’ll reach the heliopause. We’re not there yet – that’s one thing I can say with confidence.” says Ed Stone, Voyager project scientist.
Voyager 2 currently sits at the edge of the Heliosphere. The heliosphere is the bubble-like region of space dominated by the Sun, which extends far beyond the orbit of Pluto.
What the team is seeing with Voyager 2, resembles patterns seen in Voyager 1’s journey. In May 2012, Voyager 1 experienced an increase in the rate of cosmic rays similar to what Voyager 2 is now detecting. That was about three months before Voyager 1 crossed the heliopause and entered interstellar space.
However, Voyager team members note that the increase in cosmic rays is not a definitive sign that the probe is about to cross the heliopause. Voyager 2 is in a different location in the heliosheath — the outer region of the heliosphere — than Voyager 1 had been, and possible differences in these locations means Voyager 2 may experience a different exit timeline than Voyager 1.
The fact that Voyager 2 may be approaching the heliopause six years after Voyager 1 is also relevant, because the heliopause moves inward and outward during the Sun’s 11-year activity cycle. Solar activity refers to emissions from the Sun, including solar flares and eruptions of material called coronal mass ejections. During the 11-year solar cycle, the Sun reaches both a maximum and a minimum level of activity.
The Voyager spacecraft were built by NASA’s Jet Propulsion Laboratory in Pasadena, California, which continues to operate both. JPL is a division of Caltech. The Voyager missions are a part of the NASA Heliophysics System Observatory, managed by the Heliophysics Division of the Science Mission Directorate in Washington.
You can track Voyager’s progress right here.