Mankind has officially reached the heliopause.
But perhaps I should start at the beginning. Voyager 1 departed Earth in 1977, with the goal of doing a couple planetary flybys, followed by a straight-ish shot out of the solar system entirely. Three years later, it reached Saturn. The above image shows exponentially increasing distance, so if you look at Earth, then look at Saturn, it should not be surprising when I say that it is just now, 31 years after that, that Voyager is on the cusp of leaving the solar system entirely.
And even though it's been cruising for more than three decades, and is currently the fastest-moving probe in space at around eleven miles per second, it didn't become the farthest-reaching manmade object until 1998, when it finally passed Pioneer 10 (which was actually launched three years after Voyager I).
The outer "edge" of our solar system, it turns out, is determined by solar wind. Even as far out as Voyager is right now, charged particles from the sun are still blowing around. But out in what's known as the interstellar medium, there are other particles blowing back (from what? Fuck if I know). The point where winds (I love that they classify this stuff as "wind") pushing out from the sun and winds pushing in from outer space equalize is called the heliopause, and once you pass that, you are officially in interstellar space.
The trick is that when you're dealing with this kind of scale, even a "point" like the heliopause could take months or years to traverse, and there's no way to know exactly how big it is until you're through it. So while it's maybe a little too soon to start popping the champagne, we're far enough along that we can pretty safely classify Voyager 1 as the first manmade object to leave the solar system.
And with fifteen years of power left, there's still plenty of time to find a gas station.
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