Forty-one years after it launched into space, NASA's Voyager 2 probe has exited our solar bubble and entered the region between stars. Its twin, Voyager 1, made this historic crossing in 2012. Edward Stone, the Voyager mission's project scientist, and Suzanne Dodd, the mission project manager, discuss this major milestone and what's to come for the trailblazing probe.


We have ignition, and we have liftoff of the Titan-Centaur carrying the first of two Voyager spacecraft to extend man's senses farther into the solar system than ever before.

Suzanne Dodd: They were launched in 1977. That's a long time ago. We say 41 years, but it's really two generations ago. You can think of what the technology was. Your smartphone has 200,000 times more memory than what the Voyager spacecraft had.

And so it's just exciting that we've been able to get it into interstellar space.

Ed Stone: We launched two Voyager spacecraft. They're basically the same. But they were on different paths. Voyager 2 was the one that was chosen to do the Grand Tour. That is to fly by Jupiter and then Saturn and then Uranus and then Neptune.

And then after 1989 we began what is now called the Voyager Interstellar Mission. We were on a path, we

hoped, to get to reach interstellar space while we still had power on the spacecraft to transmit the data back. And that's what Voyager 1 did in 2012. And that's now what Voyager 2 is starting to do in 2018.

The Sun creates this huge bubble of plasma--ionized material goes outward at a million miles per hour and creates a bubble. And inside the bubble, most of the material has come from our Sun. And the magnetic field has come from our Sun. Outside the bubble, most of the material comes from other stars that exploded 5, 10, 15 million years ago.

We have an instrument which measures the wind coming from the Sun. And we saw that, in fact, there was no longer any measureable solar wind. We had left the bubble basically.

Dodd: The team has been looking forward for this for a long time and really working hard in an engineering sense to make this day happen and to keep the spacecraft with all the instruments on. So that all 5 instruments could sense the heliopause crossing and have data for that. What that means is that the

Voyager 2 spacecraft is now traveling in interstellar space.

Stone: Well, this just contributes to the number of discoveries that Voyager has been making. And this is one we hoped we would have the chance to do. And, fortunately, both spacecraft were still operating when they reached interstellar space. It's really quite... quite remarkable.

Voyager changed our view of the solar system really. We saw this active volcanic activity on Io. We saw the possibility of an ocean on Europa. Just time after time we were discovering things that we had not really even imagined some years before the Voyager mission. What makes it so exciting is that not only do we confirm what we thought we knew, but, even better, it tells us where we didn't know that there was something to be discovered.

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