Artist’s rendering of Voyager 1 in interstellar space. Credit: NASA.

When the Voyager 1 spacecraft was launched in 1977, it’s mission was to explore Jupiter and Saturn. But 35 years and 122 astronomical units later, the venerable probe entered interstellar space. Read that again:

We put a spacecraft in interstellar space!

Even with its nuclear batteries running down, Voyager is still doing science, taking readings of the tenuous gas at extreme distances from the sun. The Solar wind streams away from the sun at high speeds until is gets to about 100 times the distance from Earth to the Sun. At that point, it’s so spread out that it gets blocked by interstellar gas and gets swept away by the interstellar wind. Space is pretty empty to start with, but that far out, it took a whole year to get enough data to be sure that the spacecraft had crossed over into this interstellar medium. Last week, NASA announced that it had. In fact, Voyager 1 has been traveling through interstellar space–beyond the electromagnetic influence of the Sun–since August of 2012.

Let that sink in for a minute. Interstellar travel is hard. Just ask any rocket scientist. Getting anything far enough out to directly measure the interstellar medium is incredibly hard, just because it’s so far. But now Voyager is doing it.

This is history being made. The human species can now send probes clear out of our solar system. This should really be up there with landing a man on the Moon, leaving Earth’s influence to become an interplanetary civilization. Now, though unmanned, we can also leave the Sun’s influence and go interstellar.

Okay, so it’s not quite accurate to say we’ve left the Solar System. Comets fly much father away–sometimes over a light-year. But even if this is a largely symbolic gesture on those scales, it’s a pretty important one. Being able to directly interact with the Galaxy at large is no small matter. After all, that’s why we sent a message with it.