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Planetary Radio • Jan 14, 2026

IMAP and the shape of the heliosphere

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On This Episode

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David McComas

Professor of Astrophysical Sciences, Princeton University; Principal Investigator, NASA’s IMAP and IBEX missions

Matina gkioulidou portrait

Matina Gkioulidou

Johns Hopkins Applied Physics Laboratory; IMAP Project Scientist and Co-Investigator

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Sarah Al-Ahmed

Planetary Radio Host and Producer for The Planetary Society

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Bruce Betts

Chief Scientist / LightSail Program Manager for The Planetary Society

Our Solar System is wrapped in a vast, invisible bubble created by the Sun, a protective region that shields Earth and the planets from much of the radiation that fills our galaxy. But until recently, scientists have only had rough sketches of what this boundary looks like and how it behaves.

In this episode of Planetary Radio, host Sarah Al-Ahmed is joined by David McComas, professor of astrophysical sciences at Princeton University and principal investigator of NASA’s Interstellar Mapping and Acceleration Probe (IMAP) and Interstellar Boundary Explorer (IBEX) missions, along with Matina Gkioulidou, a heliophysicist at Johns Hopkins Applied Physics Laboratory, former IMAP-Ultra instrument lead, and current IMAP project scientist and co-investigator.

Now stationed at the Sun–Earth L1 Lagrange point, IMAP uses 10 instruments to study the heliosphere — the region where the solar wind collides with material from interstellar space. The mission does this by tracking energetic neutral atoms, particles that travel in straight lines from distant regions of the heliosphere, allowing scientists to map areas of space that spacecraft can’t directly sample.

McComas and Gkioulidou explain how IMAP builds on the legacy of Interstellar Boundary Explorer, what makes this mission different, and why understanding the Sun’s influence across space matters not just for fundamental science, but for space-weather forecasting and protecting technology and astronauts closer to home.

IMAP and the solar wind
IMAP and the solar wind An artist's impression of NASA's future Interstellar Mapping and Acceleration Probe (IMAP). The spacecraft will monitor space weather, investigate the "solar wind" of particles emitted by the Sun, and study the space between stars.Image: NASA / Johns Hopkins APL / Princeton University / Steve Gribben
The heliosphere
The heliosphere This illustration shows the heliosphere, the vast bubble of charged particles and magnetic fields created by the Sun as the solar wind pushes outward into interstellar space. Acting as a protective shield, the heliosphere deflects much of the harmful radiation from the interstellar medium, helping to preserve a habitable environment within our solar system. Its outer boundary is constantly changing as solar wind conditions shift and interact with the surrounding galaxy.Image: NASA / IBEX / Adler Planetarium

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