ARUN RATH, HOST:
Over a relatively short period of time, the discoveries of the Voyager spacecraft revolutionized our understanding of our solar system. Planetary scientist Jim Bell takes us through the amazing human stories behind the 40-year history of the Voyager spacecraft mission in his book "The Interstellar Age." I asked him to rank the Voyager missions in terms of the history of human exploration.
JIM BELL: Oh my gosh, that's - Voyagers are one of the grandest, most remarkable, incredible voyages of exploration that humans have ever taken. It just so happens that we're taking that voyage through the eyes of robotic travelers.
RATH: And this is a story about those robotic voyagers. But in many ways it's also a personal memoir. Your own life is intertwined with the robots.
BELL: It is. Voyagers were launched in 1977. I was born in '65. And I remember learning about them and hearing about their launches and seeing them pass Jupiter and Saturn in '79 and '80. My entrance into planetary science, which is my career now, came through getting involved with the Voyager missions as an undergraduate and a graduate student.
RATH: You described it as being almost brilliant divine luck.
BELL: It really was. You know, we have to remember that back in those days, you know, there was no Internet. And so in order to see what was happening, you know, you had to be there. And there was the Jet Propulsion Laboratory in Pasadena, Calif. And I was an undergraduate at Cal Tech, also in Pasadena, and was working for just an amazing guy named Ed Danielson, who was part of the Voyager camera team. He arranged to get me into the room where all of this action was happening, where all of these pictures were coming down in real time. And there was nowhere like that on the planet.
RATH: There are these scenes in those rooms, which are just kind of amazing, where you're receiving new information about the freaking cosmos, and you're getting it before anybody else. It's just, like, coming into you.
BELL: Yeah, and they were very stressful times and stressful places because, you know, the Voyagers were flyby spacecraft. They're not - they're not orbiters or rovers. They can't redo something, so you only get one shot. You know, if you didn't set the exposure level right on the camera, too bad. And so that stress was tangible.
RATH: Jim, I still have some of my old kids' science books from the - going back to the early '70s. And they're shocking to look at now. There're no decent pictures of anything much farther than our own moon, and so much that's just wrong. Can you give us a sense of how much the Voyager missions increased our knowledge of our own solar system?
BELL: You know, the Voyagers have literally changed the textbooks. All of these spectacular pictures that we've seen - the Great Red Spot of Jupiter, the rings of Saturn view from behind Saturn - none of that was known. They were all points of light, even in the world's largest telescopes before the 1980s. So all of a sudden - and we really felt this - we were going to transition for the first time to see these places as worlds of their own - not just dots up in the sky, but as real worlds with geology and atmospheres and histories. And as my calling colleague Larry Soderblom, who I quote in the book said, you know, you can only discover the solar system for the first time once. And that's what Voyager did.
RATH: Now, these Voyager spacecrafts, they have certainly accomplished enough in terms of what they've told us about our solar system. But the mission has now shifted. It's now the Voyager Interstellar Mission. Can you tell us about the moment when you realized Voyager may have left the solar system?
BELL: Yeah, that's right. Voyager 1 and 2 are now more than 10 billion - with a B - miles away from the Earth. And they're traveling at about 10 miles per second, about 38,000 miles per hour. They're the fastest things humans have ever sent anywhere. And you could try to imagine one of the spacecrafts passing through your neighborhood at 10 miles per second.
BELL: Wow, that thing is really moving. And yet, at those speeds, it's taken 40 years to get out near the edge of our solar system. In late 2012, the instruments saw this dramatic, sudden change like they popped out of the bubble. And all of a sudden, Voyager 1's in interstellar space. And for the first, we're making measurements and getting scientific data on what it's like between the stars - not close to a star, but between the stars. And we're still in contact with both spacecraft every day, for many hours every day.
Voyager 2 is not far behind. It's predicted to pop out of the bubble almost any time. I tried to get Ed Stone to arrange for it to happen right when my book comes out, but it hasn't happened yet. But we'll see. But it's just very exciting to be able to literally enter interstellar space. And along with the spacecrafts, we've all entered the interstellar age because of that - because now we have interstellar travelers.
RATH: That's Jim Bell, president of the Planetary Society and a professor at Arizona State University. His new book is called "The Interstellar Age: Inside The 40 Year Voyager Mission." Jim, this is fascinating, such a pleasure speaking with you. Thank you.
BELL: Great fun - great to be on the show.
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