At the edge of our Solar System lies a scorching-hot boundary — and Voyager flew right through it.
The heliopause — a thin region where the Sun’s solar wind collides with the interstellar medium — reaches temperatures between 30,000 and 50,000 Kelvin. When Voyager 1 crossed it in 2012 and Voyager 2 followed in 2018, they didn’t just survive — they thrived, becoming the first human-made objects to enter interstellar space.
But how did they make it through such intense heat?
Because while the heliopause is hot, it’s also extremely sparse. There are so few particles in this boundary zone that they don’t transfer much thermal energy, meaning the spacecraft weren’t damaged despite the searing conditions.
The data confirmed exactly what scientists had long suspected:
- The heliopause acts as the Sun’s last shield against the galactic environment.
- The solar wind is finally halted and turned back at this boundary.
- The surrounding magnetic fields outside were found to be remarkably aligned with those inside — a surprise that’s reshaping our understanding of interstellar physics.
Nearly 50 years after launch, both Voyagers continue to transmit data, deepening our insight into how the Sun’s influence fades — and where the Milky Way truly begins.
The final frontier isn’t just cold and dark — it’s also hot, thin, and full of answers.