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Voyager 1 Has Left the Solar System!

September 13th, 2013

Artist's depiction of Voyager 1 leaving our solar system. Image credit: NASA

by Jason Kendall

Voyager 1 has gone where no spacecraft has gone before. It’s left the solar system! That’s the first time ever a spacecraft has gone that far. It’s a first for humanity — a really, really big deal.

It actually reached the edge of our solar system last August but scientists were only able to confirm it recently … and made their momentous announcement yesterday.

There’s nobody on board Voyager 1, of course, but it is sending back data, even though it takes us 17 years to get the message … and even if the technology is so old from when it left 36 years ago, in 1977, that a basic handheld iPhone now stores more data.

The whole project is an amazing story. Back in 1972, around the time when some of your parents were born, scientists out at the Jet Propulsion Laboratory in California realized that all the gas giant planets would be lined up in a way that would make a trip to all four possible, but only if they launched in 1977.  So, using the best technology available at the time (including 8-track tapes, yikes!), they built two unmanned spaceships the size of small cars — Voyager 1 and Voyager 2. And sent them on their way.

In 1979, they flew by Jupiter, taking pictures that astonished the world.  They were the first close-ups of the biggest planet.

Jupiter's red spot as photographed by Voyager. Photo credit: NASA

A couple of years later they went by Saturn.

Saturn as photographed by Voyager. Photo credit: NASA

Voyager 2 went by Uranus in 1986 and Neptune in 1989.  Until the Hubble Space Telescope was launched these were the only pictures ever of these distant planets.

With the Voyagers’ batteries eventually running low, the cameras were turned off to save energy, but not after a final image in 1990.  For the last picture it turned around and looked home.  Earth was a tiny, blue dot barely visible in the glare of the Sun.

Earth, as seen from Voyager 1, four billion miles away. Photo credit: NASA

No more images, but Voyager still measures “space weather”. The Sun actually has a wind that continuously streams away.  Sometimes, the Sun belches out huge storms of charged particles — like a massive burp (pretty sure you know what we’re talking about), and sends a magnetic field out with it.  When that hits the Earth, we see the amazing Northern Lights.  These streams are so large, they go past and around the Earth, and keep going.  The Voyagers are billions of miles away and these streams make it out to where they are (though it takes weeks to get there).

As the Voyagers have travelled for nearly the past 40 years, they’ve been swept over by these waves of particles many times, like waves washing up on a shore. As these waves swept by, the Voyagers’ antennae “heard” them.

You can’t send yourself out of the solar system … but you can try this at home:  Get a radio with a long antenna.  Turn it to an AM radio station with just static or quiet music.  Now take your cell phone, or anything that you can use to communicate, and turn it on.  Now move your cell phone around near the radio antenna.  You’ll be able to hear buzzing on the radio!   The cell phone emits radio waves, and the radio detects them, just like Voyager.  Same idea.

How do we know it has left the solar system? We know because now it’s detecting different kinds of “sounds”. At the edge of our solar system, these solar wind “waves” have now met the gas particles between the stars. Scientists know the difference between the “sounds”. And that’s how they knew they were out of our solar system. Voyager 2 is nearing the edge of the solar system, as well.

The Voyagers will never come home.  They’ll continue along at a million miles a year (38,000 miles and hour, or about 17 miles every second).  It doesn’t have rockets, it is just coasting. But in the time it took you to read this, Voyager has gone an additional 1,700 miles.  The gas it’s traveling through is not thick enough to stop it.

Voyager 1’s next big moment? That should come in about 40,000 years (!) when it’s predicted to pass 3 trillion miles from the next closest star.

The batteries will long be dead, and Voyager will likely just be floating around in the vast universe. Anticipating that, scientists placed a gold record on board carrying 115 pictures, music, greetings, and sounds from Earth — like a message in a bottle. You can see what’s on it here . It’s really cool.

Perhaps one day someone from Earth, or maybe another world, will find it.

Jason Kendall is HTE’s awesome space writer. He also teaches astronomy at William Paterson University in New Jersey and does public outreach programs. Best of all, he’s happy to take your questions! You can submit them below.

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