You may have heard at some point in the past year that the spacecraft Voyager 1 has left the Solar System. You may have been confused when you heard it left the Solar System again a week later, and again a month after that, and then again and again and again. They’ve made the announcement many times, and retracted it many times as well, but this time NASA scientists are absolutely at least 98.9% positively certain Voyager really has left the Solar System.
It’s kind of hard to tell when you’ve left the Solar System because no one’s ever done it before, so no one knows where the signpost is. Finding that signpost is made more difficult by the fact that some of Voyager 1’s instruments don’t work anymore (Voyager 1 was launched in 1977).
The border between the Solar System and interstellar space is called the heliopause, and it’s the point where the Sun’s radiation gives way to the radiation of the rest of the galaxy. Determining the exact location of the heliopause may be extra important for science fiction writers. Just as rivers and mountain ranges once determined the political boundaries of nations on Earth, the heliopause may determine the political boundaries of human territory in a Sci-Fi future.
For more information on Voyager 1’s continuing mission in interstellar space, click here.
P.S.: Voyager 2 is getting close to the heliopause as well. Maybe in a few years, it will follow in its sister’s footsteps.