What does it really mean to enter interstellar space, and what have we learned since humanity first crossed the invisible boundary between our Sun and the stars?

In this episode of Planetary Radio, we explore the science of the heliosphere and the realm beyond with Linda Spilker, project scientist for the Voyager mission at NASA Jet Propulsion Laboratory. Drawing on decades of experience with the twin spacecraft, Spilker shares how Voyager reshaped our view of the Solar System’s outer frontier, from the nature of the heliopause to the unexpectedly rich structure of the local interstellar medium.

We unpack what Voyager 1 and Voyager 2 have taught us about charged particles, magnetic fields, and cosmic rays beyond the Sun’s protective bubble, and why those measurements have upended earlier ideas about where the Solar System truly ends. Spilker also reflects on the mission’s extraordinary longevity, the ingenuity required to keep the spacecraft communicating across the vastness of space, and what Voyager’s legacy means for future journeys between the stars.

Then, in What’s Up, Bruce Betts, chief scientist at The Planetary Society, places Voyager in context, showing how long-lived missions shape the bigger picture of space science and why observing longer can lead to some of our most profound discoveries.

Discover more at: https://www.planetary.org/planetary-radio/2026-voyagers-and-the-heliopause

What does it really mean to enter interstellar space, and what have we learned since humanity first crossed the invisible boundary between our Sun and the stars?
In this episode of Planetary Radio, we explore the science of the heliosphere and the realm beyond with Linda Spilker, project scientist for the Voyager mission at NASA Jet Propulsion Laboratory. Drawing on decades of experience with the twin spacecraft, Spilker shares how Voyager reshaped our view of the Solar System&rsquo;s outer frontier, from the nature of the heliopause to the unexpectedly rich structure of the local interstellar medium.
We unpack what Voyager 1 and Voyager 2 have taught us about charged particles, magnetic fields, and cosmic rays beyond the Sun&rsquo;s protective bubble, and why those measurements have upended earlier ideas about where the Solar System truly ends. Spilker also reflects on the mission&rsquo;s extraordinary longevity, the ingenuity required to keep the spacecraft communicating across the vastness of space, and what Voyager&rsquo;s legacy means for future journeys between the stars.
Then, in What&rsquo;s Up, Bruce Betts, chief scientist at The Planetary Society, places Voyager in context, showing how long-lived missions shape the bigger picture of space science and why observing longer can lead to some of our most profound discoveries.
Discover more at:&nbsp;<a href="https://www.planetary.org/planetary-radio/2026-voyagers-and-the-heliopause">https://www.planetary.org/planetary-radio/2026-voyagers-and-the-heliopause</a>

Planetary Radio brings you the human adventure across our Solar System and beyond. We visit each week with the scientists, engineers, leaders, advocates, and astronauts who are taking us across the final frontier. Regular features raise your space IQ while they put a smile on your face. Join host Sarah Al-Ahmed and Planetary Society colleagues including Bill Nye the Science Guy and Bruce Betts as they dive deep into space science and exploration. The monthly Space Policy Edition takes you inside the DC beltway where the future of the US space program hangs in the balance. Visit planetary.org/radio for an episode guide and much more.

Planetary Radio brings you the human adventure across our Solar System and beyond. We visit each week with the scientists, engineers, leaders, advocates, and astronauts who are taking us across the final frontier. Regular features raise your space IQ while they put a smile on your face. Join host Sarah Al-Ahmed and Planetary Society colleagues including Bill Nye the Science Guy and Bruce Betts as they dive deep into space science and exploration. The monthly Space Policy Edition takes you inside the DC beltway where the future of the US space program hangs in the balance. Visit planetary.org/radio for an episode guide and much more.

Planetary Radio: Space Exploration, Astronomy and Science

Planetary Radio brings you the human adventure across our solar system and beyond. We visit each week with the scientists, engineers, leaders, advocates, and astronauts taking us across the final frontier. Regular features raise your space IQ while they put a smile on your face. Join host Sarah Al-Ahmed and Planetary Society colleagues including Bill Nye, the Science Guy, and Bruce Betts, chief scientist for The Planetary Society, as they dive deep into the latest space news. The monthly Space Policy Edition takes you inside the DC beltway with Casey Dreier and Jack Kiraly to discuss the politics of space exploration in the US and advocacy actions you can take to support the missions that matter. Visit planetary.org/radio for the space trivia contest, an episode guide, and much more.

Planetary Radio brings you the human adventure across our solar system and beyond. We visit each week with the scientists, engineers, leaders, advocates, and astronauts taking us across the final frontier. Regular features raise your space IQ while they put a smile on your face. Join host Sarah Al-Ahmed and Planetary Society colleagues including Bill Nye, the Science Guy, and Bruce Betts, chief scientist for The Planetary Society, as they dive deep into the latest space news. The monthly Space Policy Edition takes you inside the DC beltway with Casey Dreier and Jack Kiraly to discuss the politics of space exploration in the US and advocacy actions you can take to support the missions that matter. Visit planetary.org/radio for the space trivia contest, an episode guide, and much more.

Linda Spilker, project scientist for the Voyager mission, explains what Voyager has revealed about the heliopause and the Solar System’s outer edge.

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