Voyager 1 has been cruising through space since 1977 — and it’s now an incredible 24 billion kilometers from Earth. Recently, it’s made headlines across the scientific world after crossing a mysterious, invisible boundary: the edge of our solar system, where solar space ends and interstellar space begins.
Wait, there’s a boundary out there?
Yes — and it’s dramatic. This region, sometimes described as a “wall of fire,” reaches scorching temperatures up to 30,000°C. If you think summer in Phoenix is hot, this place takes things to a whole new level.
This breakthrough has completely changed how scientists map the cosmos and gives strong support to a theory known as the heliopause — the line where the Sun’s influence fades and the wider galaxy begins.
Curious to learn more? Let’s dive into what this means for our understanding of the universe.
NASA new edge of the Solar System
Since its launch, Voyager 1 has flown by Jupiter and Saturn along with their moons sending back some of the most iconic images in space exploration. But its real adventure began after it left the planetary neighborhood and headed into the outermost edges of the solar system. Out there lies the heliopause a boundary where the force of the solar wind from our Sun finally evens out with the pressure of particles in deep space, known as the interstellar medium. Instead of fading into silence, Voyager 1’s instruments picked up something extraordinary: a sharp increase in temperature and a spike in energetic particle density. Scientists are calling this intense region the wall of fire.
NASA What is the heliopause?
Let’s break it down. The heliopause is essentially the outer edge of our solar system — the boundary where the Sun’s influence fades, and the vast expanse of interstellar space begins. Beyond this invisible line, the charged particles from other stars roam freely, no longer held back by the Sun’s solar wind.
So why is this important?
- The heliopause acts like a shield, protecting our solar system from some of the most dangerous high-energy cosmic rays.
- It serves as a natural space lab, giving scientists the chance to study plasma — the fourth state of matter — under extreme conditions we can’t replicate on Earth.
- It also offers clues about how a star (like our Sun) affects the planets orbiting it, especially when it comes to making those planets habitable.
Now here’s where it gets really interesting: Voyager 1’s detection of the so-called “wall of fire” confirms that even in the vast emptiness of space, where matter is incredibly sparse, collisions between stellar winds can still generate massive amounts of heat — up to 30,000°C. But because there’s so little actual matter out there, the spacecraft isn’t damaged. It’s hot, but not “touch-it-and-burn” hot in the usual sense.
A wall of fire at 30,000 °C
NASA engineers explain that the measured temperature does not correspond to heat that could burn solid material, but rather to the kinetic energy of particles traveling nearly at the speed of light.
In this extremely thin gas, collisions are so rare that passes through the region unharmed, like a true champion Voyager 1
Magnetohydrodynamic consequences
One of the most surprising findings from Voyager 1 is that the magnetic fields it’s detecting on both sides of the heliopause — inside and outside the solar system — are more alike than scientists expected.
Up until now, it was widely believed that the magnetic field in interstellar space would be very different from the one shaped by our Sun. But Voyager’s data is telling a different story.
It turns out the solar wind carries magnetic field lines far into space. When these lines get squeezed or compressed near the edge of the solar system, they create what scientists call a “magnetic reconnection zone.” This zone acts like a cosmic transformer, converting the energy of moving particles (kinetic energy) into heat.
In short: space out there is even more dynamic and interconnected — than we thought.
Voyager 1: a relic still making history
After 48 years in space, Voyager 1 is a true veteran of exploration. It’s still going — even though each of its instruments now runs on just about 4 watts of power (less than an LED nightlight!). Its plutonium-based batteries lose a little energy every year, but NASA’s engineers are determined to keep it alive. They’ve carefully managed its power supply to keep the most critical instruments — like the plasma and cosmic ray detectors — running.
Of course, at such an extreme distance, communication isn’t easy. Signals from Voyager 1 grow weaker as they travel across billions of kilometers. To catch them, NASA relies on enormous 70-meter-wide antennas and incredibly sensitive receivers.
And Voyager’s journey isn’t over yet. NASA hopes to keep it going until at least 2030. The question now is — can this space pioneer survive just a little longer?
After 48 years in space, Voyager 1 is a true veteran of exploration. It’s still going — even though each of its instruments now runs on just about 4 watts of power (less than an LED nightlight!). Its plutonium-based batteries lose a little energy every year, but NASA’s engineers are determined to keep it alive. They’ve carefully managed its power supply to keep the most critical instruments — like the plasma and cosmic ray detectors — running.
Of course, at such an extreme distance, communication isn’t easy. Signals from Voyager 1 grow weaker as they travel across billions of kilometers. To catch them, NASA relies on enormous 70-meter-wide antennas and incredibly sensitive receivers.
And Voyager’s journey isn’t over yet. NASA hopes to keep it going until at least 2030. The question now is — can this space pioneer survive just a little longer?
What comes after the wall of fire?
The probe will continue measuring the density of particles and magnetic fields in the interstellar medium. This data will help refine models of the heliosphere’s structure and prepare for future manned missions beyond Pluto!
Voyager 1’s crossing of the “wall of fire” has been a milestone. Now it’s up to NASA to open new paths of interstellar exploration. What lies beyond?
NASA’s Voyager spacecraft revealed a remarkable discovery at the edge of our solar system: a vast region of superheated plasma, reaching temperatures between 30,000 and 50,000 Kelvin.
This area, encountered by both Voyager 1 and Voyager 2 as they crossed the heliopause, the… pic.twitter.com/dnec4HmTzY
— Erika (@ExploreCosmos_) June 12, 2025