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Hank Green: The twin voyager spacecraft were launched 35 years ago in the summer of 1977 with the mission of exploring Jupiter and Saturn, and they're still going strong. They don't get much press these days, and you might have even forgotten that they were out there, but they're still doing some awesome science. Voyager II went on to Uranus and Neptune and it remains the only craft to have ever visited those planets.

Voyager I on the other hand, was given a different objective. Deep space, and it alone will take humanity's reach further than it's ever gone, possibly further than it will ever go. So in honor of its 35 years of service, here are three things that you probably didn't know about Voyager I.

One, it's about to become the first man-made object to leave the solar system, if it hasn't already, that is. As we speak, Voyager I is more than 18 billion km from Earth, that's about 3.5 billion km farther than Voyager II, and it's hurtling through space at more than 61,000 km/hour. NASA scientists think that it's probably in the heliosheath, which is the outermost layer of the heliosphere, the bubble of charged particles given off by the sun that surrounds the solar system. They're predicting that it will officially reach interstellar space sometime between now and 2015.

Two, it's still recording and sending back data, even though its primary mission ended in 1980, Voyager I is still very much operational, and we're still learning from it. Six of its eleven original instruments are still working, including the equipment that measures magnetic fields and cosmic radiation and ultraviolet emissions. In March of 2011, the spacecraft was re-positioned for the first time in 21 years to better study the behavior of charged particles in deep space. Three months later, NASA said Voyager's observations suggested that the edge of the solar system is not smooth, but rather filled with what they called "a turbulent sea of magnetic bubbles", millions of kilometers wide. And in December of 2011, it made its first ever observation of ionized hydrogen emissions from the Milky Way, an observation astronomers use with other galaxies to determine their rate of star formation. Keep 'em coming, V-ger.

Three, it still has between eight and fifteen years to go. Voyager's powered by the natural decay of plutonium-238 and makes for a pretty awesome long-lasting battery, but it loses about four watts of power every year. So, it has enough electrical power and thruster fuel to keep working until at least 2020, but NASA plans to turn off all the instruments by 2025. Once that happens, when it's 48 years old and 20 billion km from Earth, Voyager I will spend eternity as a floating beacon in space. You've probably heard of the famous golden record it's carrying to tell other civilizations about us. It has thousands of recordings of sounds and greetings from our world leaders, all kinds of music and also tons of crazy pictures of airplanes, supermarkets, traffic, animals, human anatomy, and demonstrations of how to lick ice cream. Seriously.

So Voyager I, thanks for everything you've done and everything you have yet to do, forever. And also, thank you for watching this episode of SciShow. If you have any ideas or questions or comments, please leave them down below in the YouTube comments or on Facebook or Twitter, and we'll see you next time.

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