Launched in August 1977 prior to the departure of its sister ship, Voyager 1, NASA’s Voyager 2 space probe exits the heliosphere, the region where the solar wind from Earth’s sun has more influence than the interstellar medium between stars. Unlike Voyager 1, Voyager 2’s plasma science instruments are still working, so the instrument readings indicating a dramatic change in local space are very clear to the vehicle’s ground controllers (Voyager 1’s exit from the heliosphere in 2012 had been much more ambiguous at first). At over eleven billion miles from the Earth, radio signals take more than 16.5 hours to reach or be received from Voyager 2 at the time of its entry into the interstellar medium, and it is expected to return science data through the 2020s. It will pass within two years of the star Ross 248 in 40,000 years.
