In this edition of Cosmically Curious, host Patrick McNamee King speaks with UNH astronomer John Gianforte about what NASA’s Voyager probes are encountering across the universe 50 years into their mission — and why mapping the boundary of interstellar space matters for the future of space travel.
Transcript:
Patrick McNamee King: So, John, last week we talked about the cool plutonium generators powering Voyager 1 and 2. You mentioned they need their own power supply because they're so far away from the Sun that solar panels aren't useful anymore. How far away are we actually talking?
John Gianforte: 16 billion miles.
Patrick: Wild. So what are they observing out there right now?
John: Right now, they have two instruments left that are still working: a magnetometer and a plasma instrument that measures charged particle density in space.
Patrick: What does that actually mean?
John: The sun emits a wind of high-energy charged particles — mainly electrons and protons — and it's been doing that ever since it formed 4.5 billion years ago. That solar wind blows outward at roughly 400 kilometers per second, ebbing and flowing depending on solar activity.
At the distance where the spacecraft are now, that solar wind has become so weak that the interstellar wind is actually more powerful. They're measuring the density of that environment to see how it changes as they travel farther into interstellar space.
Patrick: That sounds pretty cool, but why is that something we need to measure?
John: If we ever want to send spacecraft into deep space, it's essential to understand the environment they'll be operating in. It’s a fundamental effort to learn what interstellar space is really like, especially if humanity hopes to travel routinely into interstellar space someday.
If you have questions about the night sky, send us an email at cosmic@npr.org.
