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Voyager_s Final Discovery Before Leaving the Solar System · Boring Science

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Speaker 1: Voyager one detected something impossible at the edge of our
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solar system, a wall of superheated plasma reaching temperatures of
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ninety thousand degrees fahrenheit, hot enough to vaporize any known
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material instantly. Yet the spacecraft sailed right through it, instruments
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still functioning, still transmitting data back across billions of miles
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of empty space. What scientists found at that boundary changed
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everything we thought we knew about where our Solar System
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ends and true interstellar space begins. On August twenty fifth,
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twenty twelve, at precisely one hundred twenty one astronomical units
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from the Sun, Voyager one's instruments recorded something extraordinary. The
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steady stream of particles from our Sun, particles that had
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surrounded the spacecraft for its entire thirty five year journey,
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suddenly dropped, not gradually, not over weeks or months. Within hours,
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solar particles decreased by a factor of one thousand. At
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the exact same moment, cosmic rays from distant supernova explosions
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increased by nine percent. The spacecraft had crossed a threshold
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that no human made object had ever reached before. If
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you find comfort in these gentle explorations of space and science.
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I'd be grateful if you'd consider subscribing and giving this
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video alike. I'd love to know where you're watching from
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and what time it is for you.
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Speaker 2: Feel free to drop your.
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Speaker 1: Location and time in the comments below. But here's what
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makes this discovery truly unsettling. Scientists didn't immediately realize what
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had happened. The data was confusing, contradictory. Even some instruments
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suggested Voyager had entered interstellar space, others indicated it was
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still within the Sun's domain. It took nearly a year
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of analysis, debate, and additional measurements before NASA finally announced that, yes,
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Voyager one had left the Solar System, not because the
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evidence was unclear, but because what the spacecraft found at
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that boundary defied every prediction scientists had made. Think about
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what this means for a moment. We've been studying the
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Sun for centuries. We've sent dozens of space throughout the
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Solar System. We've mapped planetary orbits with extraordinary precision, predicted
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eclipses thousands of years in advance, and calculated the gravitational
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influence of objects billions of miles away. Yet when we
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finally reached the edge. When we send our most sophisticated
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instruments to measure the boundary itself, we discovered we'd gotten
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it fundamentally wrong. The region Voyager encountered isn't smooth or gradual.
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It's turbulent, violent, and far more complex than anyone imagined.
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The temperature readings alone should have been impossible. Inside our
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Solar system, temperatures decrease as you move away from the
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Sun basic physics. Yet at the heliopause, the actual boundary
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between solar and interstellar space, temperatures spike to tens of
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thousands of degrees. Not everywhere, mind you. The heat comes
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in patches, creating a chaotic mosaic of superheated plasma next
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to regions that are relatively cool. Scientists started calling it
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the wall of fire, though that name barely captures the
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strangeness of what's actually happening there. Now you might wonder
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how a spacecraft survives temperatures that would instantly vaporize steel.
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The answer reveals something fundamental about the nature of space itself.
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Temperature measures the average kinetic energy of particles, how fast
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they're moving, how violently they're vibrating, But in the near
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perfect vacuum at the edge of the Solar system, there
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are so few particles that and even though each individual
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particle carries enormous energy, they're so spread out they can't
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transfer that heat effectively. Voyager passes through this inferno like
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a ghost through walls, barely touched by the extreme conditions
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surrounding it. But the temperature anomaly was just the beginning
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of the surprises. The spacecraft's magnetometer detected something equally baffling.
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Based on decades of theoretical work, scientists predicted that the
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magnetic field beyond the heliopores would point in a significantly
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different direction than the magnetic field inside our solar system.
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Every model, every simulation, every calculation suggested this should be true.
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When Voyager one crossed the boundary, the magnetic field remained
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parallel to the solar magnetic field, exactly parallel, as if
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the boundary didn't exist at all, at least not magnetically.
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Voyager two confirmed this six years later when it made
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its own crossing at one hundred nineteen astronomical units. Same result,
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same inexplicable alignment. Scientists are still struggling to understand why
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the magnetic field is supposed to change direction at this boundary.
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That's what the physics predicts, that's what should happen. But
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it doesn't, and nobody can explain why the magnetic fields
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on both sides of this cosmic border behave as if
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they're connected aligned following rules we haven't discovered yet. Let
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me take you back to how we even knew where
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to look.
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Speaker 2: For this boundary.
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Speaker 1: The story starts in two thousand and four, eight years
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before Voyager one's historic crossing. The spacecraft had been traveling
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outward for twenty seven years at that point, moving through
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a region scientists thought was relatively well understood. Then, on
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December sixteenth, Voyager one's instruments detected an abrupt change. The
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solar wind, that constant stream of charged particles flowing outward
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from the Sun at roughly a million miles per hour,
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suddenly slowed down, not gradually, abruptly, within a matter of days,
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the solar wind went from supersonic to subsonic. This region
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became known as the Termination Shop, and it was the
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first major surprise. Scientists expected the solar wind to slow down,
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but they expected it to slow to maybe a few
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hundred thousand miles per hour. Instead, Voyager measured speeds that
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were drastically lower. In some cases, the wind seemed to
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be flowing backward toward the Sun. That shouldn't happen. The
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Sun's radiation pressure pushes everything outward always, Yet here was
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direct evidence of solar wind moving in the wrong direction.
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Three years later, Voyager two hit its own termination shock
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at eighty three point seven astronomical units, different location, different
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distance from the Sun. This told scientists something crucial. The
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Solar System isn't a perfect sphere. It's lopsided, compressed on
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one side, elongated on the other. The Sun is moving
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through interstellar space about twenty six kilometers per second, and
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that motion creates a shape more like.
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Speaker 2: A comet than a bubble.
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Speaker 1: The leading edge, where we're pushing through the interstellar medium,
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is compressed and closer to the Sun. The trailing edge
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stretches out behind us for potentially thousands of astronomical units.
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But the termination shock revealed other mysteries to the magnetic
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field behavior was bizarre inside the Solar System. As the
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Sun rotates every twenty six days, the direction of the
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interplanetary magnetic field alternates every thirteen days. This creates a
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pattern's scientists described as zebra stripes, alternating bands of magnetic
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polarity move an outward with the solar wind. Before the
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termination shock, these stripes passed Voyager quickly. After crossing the shock,
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the patterns slowed down dramatically. It took more than one
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hundred days for a single stripe to pass the spacecraft.
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The solar wind had slowed down that much. And then
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there was the cosmic ray mystery. Scientists predicted the cosmic rays,
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high energy particles from distant super and nova explosions, would
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reach their maximum intensity at the termination shock. These particles
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are constantly trying to penetrate into our solar system, but
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the solar wind pushes back against them. At the shock,
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where the solar wind slows down dramatically, scientists expected cosmic
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rays would pile up, creating an intense radiation zone.
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Speaker 2: That's what Voyager found.
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Speaker 1: The intensity of cosmic rays at the shock was lower
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than expected, and as Voyager moved beyond the shock, deeper
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into the region between the shock and the heliopause, the
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cosmic ray intensity kept increasing. It's still increasing today, even
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though Voyager is now well into interstellar space. This suggests
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something profoundly strange. There's a source of cosmic rays somewhere
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in the outer Solar System that we haven't identified yet.
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Maybe it's at the heliopause itself, maybe it's in the
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region beyond. But these particles are being generated or accelerated
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by some process we don't understand in a location we
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can't precisely pinpoint. Between two thousand and four and twenty twelve,
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Voyager one traveled through what scientists call the helios heath,
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the region between the termination shock and the heliopause. This
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is where things got really weird. In twenty eleven, the
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spacecraft entered what researchers later termed the stagnation region. Solar
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wind speeds dropped to nearly zero. Particles that should have
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been streaming outward from the Sun were instead moving inward.
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The magnetic field strength doubled. It was as if interstellar
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space was pushing back against our Solar System, creating a
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zone of compression and confusion where the rules stopped making sense.
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Scientists hadn't predicted this region. It didn't appear in any
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of the models. Yet there it was a vast zone
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spanning multiple astronomical with the solar wind essentially stalled out,
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trapped between the outward pressure from the Sun and the
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inward pressure from interstellar space. Some researchers started calling it
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cosmic purgatory, a fitting name for a region that seemed
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to belong neither to our Solar system nor to the
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space beyond it. And throughout this entire journey, Voyager was
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measuring something else that would prove crucial for determining when
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it actually crossed into interstellar space. The spacecraft carries an
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instrument called the Plasma Wave Subsystem, essentially two thirty foot
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antennas sticking out behind it like bunny ears. This instrument
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can detect oscillations in the plasma surrounding the spacecraft. When
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solar eruptions send shock waves through space, the plasma rings
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like a bell, vibrating at a frequency that depends on
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how dense it is. The denser the plasma, the higher
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the frequency. For years, this instrument detected only sporadic bursts
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brief moments when solar storms sent ripples through the helio sheath.
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But on April ninth, twenty thirteen, eight months after Voyager
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had supposedly crossed the heliopause, the instrument began detecting continuous
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oscillations at two point six killer herds. This frequency corresponded
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to a plasma density about eighty times higher than what
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Voyager had measured in the helio sheath. That's exactly the
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density jump you'd expect when crossing from the solar dominated
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heliosphere into the interstellar dominated medium beyond. This measurement became
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the smoking gun. The particle data suggested Voyager had crossed
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the boundary. The magnetic field data created confusion, but the
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plasma density measurement provided the conformation scientists needed. Voyager one
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had indeed entered interstellar space on August twenty fifth, twenty twelve.
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It just took us eight months to figure it out,
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because we had to wait for a solar storm strong
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enough to make the interstellar plasma ring clearly enough for
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our instruments to detect. Six months after that first detection,
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the plasma rang again, louder this time and add an
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even higher frequency. The density was increasing, Voyager was moving
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deeper into interstellar space, and the space itself was getting thicker,
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more substantial, more resistant. This wasn't supposed to happen either.
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Most models predicted relatively uniform conditions in the local interstellar medium. Instead,
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Voyager found that the density continues to climb the farther
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it travels from the heliopause. By October twenty twenty, both
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voyagers were reporting significant and unexpected density increases. The measurements
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implied that this wasn't just a local phenomenon around the heliopause.
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The entire region of space in front of our Solar system,
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in the direction we're moving through the galaxy appears to
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be denser than the regions to the sides or behind us.
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Scientists call this the very local interstellar medium, or v
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el ism, and we're discovering that it has large scale
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structures we never suspected existed. What makes all of this
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particularly fascinating is that we're not just learning about the
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edge of our Solar system. We're learning about the nature
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of the space between stars throughout the entire galaxy. Every
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star creates its own heliosphere, Every stellar wind pushes against
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the interstellar medium in exactly this way. By studying our
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local boundary in such detail, we're developing models that apply
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to stellar systems across the cosmos, and the discoveries keep coming.
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In twenty twenty, Voyager one's magnetometer registered an abrupt jump
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in magnetic field intensity. At the same time, plasma density
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measurements spiked upward. Scientists initially thought these were caused by
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shock waves from solar eruptions propagating through interstellar space, but
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the anomalies didn't stop. They continued for months, then years.
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Some mission scientists now suspect these persistent changes might not
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be coming from the Sun at all. They might represent
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some new type of interstellar structure that Voyager is encountering
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as it travels deeper into the space between stars. Were
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now at a remarkable point in the mission. Voyager one
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is currently one hundred seventy two astronomical units from Earth,
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the most distant human made object in existence. Voyager two
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trails behind at one hundred forty three astronomical units. Spacecraft
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are still operational, still transmitting data, still making discoveries about
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a realm that no instruments had ever directly sampled before.
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The signals from Voyager one take over twenty three hours
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to reach Earth traveling at the speed of light. Commands
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sent from Earth take another twenty three hours to reach
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the spacecraft. We're having a conversation with our most distant
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ambassador at a pace of nearly two days per exchange,
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but we're running out of time. The plutonium that powers
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both spacecraft is steadily decaying. Engineers estimate that by the
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mid two thousands and thirties, there won't be enough power
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left to run even a single scientific instrument. The voyagers
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will continue their journey into the galaxy, silent and dark,
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carrying their golden records, Humanity's message to any intelligence that
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might one day find them. But before that happens, before
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we lose contact with these extraordinary machines forever, they have
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more to tell us about the boundary they crossed and
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the strange new realm they're exploring. What they found at
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that wall of fire is forcing scientists to completely rethink
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how our solar system interacts with the galaxy at large.
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The source of those cosmic rays wasn't where anyone predicted
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it would be. Think about what voyager scientists expected to
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find the termination shock, that first major boundary where the
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solar wind slams into the interstellar medium, should have been
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the cosmic ray factory. Particles bouncing back and forth across
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that turbulent interface, gaining energy with each pass like a
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cosmic pinball machine. By the time Voyager one reached it
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in December two thousand and four, models confidently predicted the
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cosmic ray intensity would peak right there at ninety four
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astronomical units from the Sun. Instead, the intensity kept climbing
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past the shock, through the helio sheath all the way
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to the heliopause and beyond. The cosmic rays are still
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intensifying today, nearly two decades after Voyager one crossed that
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first boundary. Something out there, in the unexplored regions of
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the outer Solar System, or perhaps in interstellar space itself,
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is accelerating particles to extraordinary energies in the ways we
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don't understand. But the cosmic ray mystery was just one
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of three fundamental surprises waiting at the termination shock. The
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second involved the solar wind itself. Picture a stream of
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charged particles racing away from the Sun over a million
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miles per hour. That's the solar wind in the inner heliosphere,
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a supersonic gale of plasma that shapes magnetic fields and
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buffets everything in its path. When this wind hits the
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termination shock, it should decelerate to subsonic speeds. Models predicted
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it would slow to a few hundred thousand miles per hour.
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What did Voyager measure speeds far lower than that. At times,
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the solar wind appeared to nearly stop, even stranger, It
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sometimes seemed to flow backward toward the Sun. The wind
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that had blown outward for ninety four astronomical units was
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suddenly hesitating, stuttering, even reversing direction. Scientists found themselves looking
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at data that shouldn't exist. The solar wind was behaving
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like a river that suddenly forgot which way it was
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supposed to flow. The magnetic field added its own layer
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of strangeness. As the Sun rotates every twenty six days,
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the interplanetary magnetic field alternates direction every thirteen days. This
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creates a pattern scientists call it the zebra stripe pattern,
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moving outward with the solar wind inside the termination shock.
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These stripes passed Voyager relatively quickly as the spacecraft moves
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through them. Beyond the shock, the zebra moved at nearly
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the same speed Voyager itself. It took over one hundred
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days for a single stripe to pass the spacecraft. The
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magnetic field was switching directions in slow motion, as if
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time itself had thickened in that region. None of this
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matched the models. Scientists had built sophisticated computer simulations of
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the heliosphere's outer reaches. They'd incorporated decades of solar wind observations,
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magnetic field measurements, and plasma physics theory. The models were elegant,
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mathematically rigorous, and apparently wrong about some fundamental aspects of
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how this boundary region actually behaves. By late twenty eleven,
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Voyager one had traveled another nineteen astronomical units beyond the
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termination shock. That's when it did discovered something nobody had
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predicted at all, a region scientists would later call cosmic purgatory.
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The formal name is the stagnation region, but that clinical
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term doesn't capture the strangeness of what Voyager found. This
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was a zone where the rules seemed to shift, where
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the Solar System's influence an interstellar space's presence created something
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entirely unexpected. Charge particles streaming from the Sun were slowing
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down and turning inward. The Solar System's magnetic field doubled
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in strength, as if interstellar space itself was pressing inward,
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compressing everything. Energetic particles that originated in the Solar System
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declined by nearly half. Meanwhile, high energy electrons from outside
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increased a hundredfold. Voyager had entered a boundary layer eight
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astronomical units thick, a transitional zone that wasn't quite solar
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and wasn't quite interstellar. It was both and neither, a
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hybrid region where two domains met and mixed in ways
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the models had never anticipated. The stagnation region's inner edge
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sits approximately one hundred thirteen astronomical units from the Sun.
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Eight astronomical units might not sound like much. It's roughly
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the distance from the Sun to Saturn, but at this
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scale that's a massive zone of space, exhibiting behavior that
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challenged fundamental assumptions about how heliospheres work. What happens when
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you need to confirm you've entered interstellar space. But the
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instrument designed to measure plasma died thirty years ago. Voyager
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one's plasma science instrument failed back in nineteen eighty, long
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before the spacecraft reached the outer Solar System. This instrument
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was supposed to directly measure the properties of charged particles
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their density, temperature, and velocity. Without it, scientists had no
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straightforward way to detect the dramatic density increase that defines
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the heliopause. They needed another method, something indirect, clever. The
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answer came from those bunny ear antenres to ten meter
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probes extending behind the spacecraft as part of the plasma
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wave subsystem. This instrument wasn't designed to measure plasma density directly.
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It was built to detect waves and oscillations in the
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plasma around on the spacecraft. But in April twoenty thirteen,
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nearly eight months after Voyager's instruments suggested it had crossed
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the heliopause, those antennas picked up something remarkable, a tone,
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a pure frequency at about two point six killer herds.
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Scientists recognized what they were hearing. When plasma is disturbed
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by a solar eruption sending shock waves through space, for example,
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it rings like a bell at its natural frequency. The
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electrons oscillate back and forth along magnetic field lines, and
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that oscillation frequency depends directly on how tightly packed those
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electrons are. The frequency Voyager detected corresponded to an electron
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density of zero point zero eight particles per cubic centimeter.
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That might sound sparse, and it is, but it's eighty
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times denser than the Solar system's normal heliosphere. The definition
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of the heliopause is based precisely on this kind of
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density jump. Voyager was hearing interstellar space ring. Six months later,
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another whistle appeared. This one was louder and higher pitched.
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The density had increased further. The interstellar medium was getting
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thicker as Voyager traveled deeper into it. These plasma waves
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provided scientists with a continuous measure of density changes in
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interstellar space. As Voyager pushed farther from the heliopause, the
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waves kept coming, sometimes triggered by solar storms whose shockwaves
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followed the spacecraft into interstellar space, sometimes from sources. Scientists
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are still trying to identify. Each detection refined understanding of
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the boundary Voyager had crossed. Each measurement revealed more about
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the structure of the space beyond. But perhaps the most
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unsettling discovery came from comparing the two crossings Voyager one
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in twenty twelve and Voyager two in twenty eighteen. They
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should have been similar. Both spacecraft were built identically, both
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carried the same instruments, both crossed at nearly the same
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distance from the Sun one hundred twenty one point six
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astronomical units for Voyager one one hundred nineteen astronomical units
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for Voyager two. That consistency seemed to suggest the heliopause
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maintained a relatively stable position, except the crossings happened under
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completely different solar conditions. Voyager one cross during solar maximum,
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when the Sun's activity peaks. Voyager two crossed during solar minimum,
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when the Sun is at its quietest. Scientists expected these
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different solar conditions to produce measurably different boundary characteristics, and
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they did just not in ways anyone anticipated. Voyager one
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observed the solar wind dropping to nearly zero as it
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approached the heliopause. The wind essentially died before the crossing,
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but Voyager two measured relatively high solar wind speeds almost
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all the way through until the moment it crossed the boundary.
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Voyager two's data suggested a thinner, smoother heatlause than what
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Voyager one encountered. Both spacecraft apparently traversed the boundary in
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less than a day, but the character of that crossing
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differed significantly. The magnetic field alignment provided yet another puzzle.
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Scientists expected the interstellar magnetic field to be oriented differently
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from the solar magnetic field. These are two independent magnetic
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structures meeting at a boundary, there's no reason they should align.
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Voyager one found them largely parallel. When Voyager two crossed
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six years later, it confirmed the same surprising result. The
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magnetic fields on both sides of the heliopause were aligned
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in the same direction. This is one of those findings
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that sounds technical but carries found implications. The mechanism that
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could produce this alignment isn't understood. The physics that would
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allow two independent magnetic fields to coordinate across a boundary
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without any obvious coupling mechanism remains mysterious. Scientists must come
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to some understanding of why this happens. The current models
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don't explain it. The observations from other missions don't predict it.
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It's a fundamental feature of the heliosphere's boundary that the theories
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got wrong. Then there's the particle leakage. The heliopause isn't
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supposed to be permeable. It's the boundary where the solar
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winds pressure balances the interstellar medium's pressure. That definition suggests
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a clear demarkation solar parts on one side interstellar particles
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on the other. Reality is messier. Voyager detected interstellar particles
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inside the heliosphere on two separate occasions before crossing the boundary.
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The mission team attributed these detections to interstellar flux tubes,
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structures where the magnetic field allows particles to penetrate deeper
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than they should. If the heliosphere is like a ship
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sailing through interstellar space, the hull appears somewhat leaky. Voyager's
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instruments showed particles from inside the heliosphere slipping through the
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boundary into interstellar space. The leakage isn't uniform. Voyager one
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exited near the heliosphere's front, where the boundary seems more robust.
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Voyager two crossed closer to the flank region, appears more porous.
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This asymmetry matters. It reveals that the heliopause isn't a
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simple spherical boundary. It has structure variation regions of different permeability.
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The heliosphere itself has a shape more complex than early
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models suggested. Both spacecraft also recorded increased plasma density before
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and after crossing the boundary. The density increase on the
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solar side suggests compression the solar wind piling up against
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the barrier. The density increase on the interstellar side suggests
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the same thing in reverse, the interstellar medium compressing against
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the heliospheres outer surface. This double compression creates a boundary
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layer where both domains press against each other with measurable force.
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The higher than expected density on the interstellar side indicates
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that interstellar pressure may be shaping the heliosphere more actively
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than models predicted. The temperature dynamics at this boundary exceed
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anything scientists expected. Near the heliopores, charged particles become trapped
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and compressed. This compression generates heat, extraordinary heat. Temperatures reach
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thirty thousand to fifty thousand kelvin in some regions. That's
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fifty four thousand to ninety thousand degrees fahrenheit, hot enough
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to ionize nearly anything, hot enough to create what some
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researchers have called the wall of fire. But here's the
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remarkable part. The particle density is so low that this
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heat doesn't transferred to spacecraft. Voyager passed through these super
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hot regions without any thermal damage.
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Speaker 2: The heat exists, but it exists.
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Speaker 1: In such a sparse medium that it can't effectively conduct
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to solid objects. The temperature isn't uniform either, nearby regions
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remain relatively cooler. The boundary creates a patchwork of hot
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and cold plasma, unlike anything observed inside the heliosphere. The
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temperature variations are extreme and patchy, far more chaotic than
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models predicted. As Voyager approached the heliopause, its instruments recorded
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sudden changes in particle density and magnetic fields. These weren't
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the smooth, gradual transitions scientists expected. They were abrupt shifts,
37:58
almost like stepping across threshold. The boundary between solar and
38:03
interstellar space turned out to be sharp in some ways,
38:07
fuzzy in others, and structured in ways nobody had fully anticipated. Now,
38:14
both voyagers continue deeper into interstellar space, and the discoveries
38:20
keep coming. The density continues to rise, the magnetic field
38:26
measurements keep revealing unexpected patterns. The persistent anomalies that began
38:34
in twenty twenty still haven't been fully explained. Scientists are
38:40
piecing together what these measurements mean for our understanding of
38:47
how stars interact with the galaxy at large. The instruments
38:52
paint a picture of interstellar space that nobody anticipated. Voyager's
38:58
plasma wave instrument, those two bunny ear antennas extending thirty
39:04
feet behind the spacecraft started picking up something strange. In
39:08
April twenty thirteen, a tone, a persistent hum. The electrons
39:15
in the interstellar plasma were ringing like a struck bell,
39:19
vibrating at two point six killer hertz. This frequency revealed
39:24
something critical about the density of the space voyager had entered.
39:30
Speaker 2: The pitch of the.
39:30
Speaker 1: Ringing directly correlates to how tightly packed the electrons are.
39:35
Higher frequency means higher density. Inside the heliosphere, the density
39:41
measured about zero point zero zero one electrons per cubic centimeter,
39:48
sparse empty. The plasma wave instrument rarely detected anything worth noting,
39:55
just occasional bursts when solar eruptions sent shock waves rippling
40:00
outward beyond the heliopause. That two point six killer herz
40:05
tone indicated a density of zero point zero eight electrons
40:10
per cubic centimeter, eighty times denser than the heliospheres interior.
40:18
This density jump wasn't just confirmation of the crossing. It
40:23
fundamentally defined what the heliopause is. The boundary exists precisely
40:30
where this density transition occurs. The sharp increase in particle
40:35
concentration creates the physical barrier between solar and interstellar domains.
40:41
Six months later, the tone changed again, louder, higher pitched.
40:48
The interstellar medium was getting thicker fast. Before Voyager, scientists
40:54
had only theoretical models to predict interstellar density. Now they
41:00
had measurements, real data from beyond the edge. The measurements
41:06
revealed something unexpected. Density wasn't constant, It varied. The plasma
41:13
wave instrument detected continuous emissions where it previously only caught
41:18
sporadic bursts. These persistent waves provided an ongoing measure of
41:24
local conditions as Voyager traveled deeper into interstellar territory. The
41:31
discovery raised immediate questions. Why was density increasing so rapidly,
41:39
What structures existed in the very local interstellar medium that
41:44
could create these variations. By October twenty twenty, both voyagers
41:50
were reporting significant density increases. The measurements implied something profound
41:57
about the regions surrounding our solaces system. The density gradient
42:02
wasn't just local noise. It appeared to be a large
42:06
scale feature of the very local interstellar medium, particularly in
42:12
the direction of the heliospheric nose, the leading edge of
42:17
our solar system's motion through the galaxy. Think about what
42:22
this means. Our Solar system isn't traveling through uniform space.
42:28
We're moving through a structured medium with varying density, pressure,
42:34
and composition. The local interstellar cloud through which we're currently
42:39
passing has internal architecture regions of compression, zones of rarefaction
42:48
gradients that shift over distances measured in astronomical units. The
42:53
cosmic rays tell another story entirely. For six years before
42:58
crossing the heliopause, Voyager one measured a steady rise in
43:03
high energy particle collisions cosmic rays with energies above seventy
43:09
million electron vaults. These particles originated far beyond our solar system,
43:15
accelerated by supernova explosions and other violent galactic events. Then
43:21
came late August twenty twelve, the cosmic ray intensity spiked sharply. Simultaneously,
43:30
low energy particles from the Sun dropped by a factor
43:34
of one thousand. August twenty fifth, twenty twelve, the day
43:39
everything changed, Voyager one recorded a one thousandfold decrease in
43:45
charged solar particles. At the same moment, galactic cosmic ray
43:50
intensity increased by nine percent. The shift was dramatic, unmistakable
43:56
solar particles streamed away into interstate space, galactic particles flooded
44:03
in from beyond. This particle swap provided some of the
44:07
clearest evidence that Voyager one had crossed into a fundamentally
44:13
different environment. The heliosphere had been filtering these cosmic rays,
44:20
blocking more than seventy percent of the galactic radiation that
44:26
would otherwise reach Earth's orbit. Voyager two's crossing revealed additional
44:32
complexity just beyond the heliopause. It discovered a boundary layer
44:37
where low energy particles still streamed outward along magnetic field lines.
44:43
Cosmic ray intensities in this layer reached only ninety percent
44:49
of levels measured farther out, a transition.
44:52
Speaker 2: Zone, not a clean break.
44:55
Speaker 1: The heliopause isn't a wall, It's a gradient with structure
45:00
region where solar and interstellar influences blend and compete before
45:05
one domain finally dominate. The cosmic ray measurements also exposed
45:11
something unexpected about their origins. Scientists had predicted that interstellar
45:18
ions would bounce back and forth across the termination shock,
45:23
slowly gaining energy with each bounds, until they became high
45:28
speed cosmic rays. The intensity of these accelerated particles should
45:35
have peaked at the shock itself.
45:38
Speaker 2: It didn't.
45:39
Speaker 1: Cosmic ray intensity failed to reach maximum at the termination shock. Instead,
45:47
it kept increasing as Voyager traveled farther beyond the shock.
45:52
The measurements suggested the source of these particles lay in
45:56
a region of the outer Solar System yet to be discovered,
46:01
somewhere between the termination shock and the heliopause, or perhaps beyond.
46:07
Cosmic rays were being accelerated by mechanisms. Scientists didn't fully
46:13
understand the magnetic field behavior proved equally puzzling. Both voyagers
46:21
carried magnetometers designed to measure field strength and direction. Scientists
46:27
expected dramatic changes when the spacecraft crossed into interstellar space.
46:34
The interstellar magnetic field should differ significantly from the heliospheric
46:40
field in both magnitude and orientation. Voyager I crossed in
46:46
twenty twelve, its magnetometer showed the interstellar field aligned largely
46:52
parallel to the heliospheric field, strange but perhaps explicable as
46:59
a local and non or measurement artifact. Voyager two crossed
47:04
in twenty eighteen at a different location during different solar conditions.
47:11
Its magnetometer confirmed the same result, the interstellar field remained
47:17
parallel to the heliospheric field. This alignment contradicted predictions based
47:24
on observations from other missions and theoretical models. The magnetic
47:30
field should have rotated, twisted, or at least changed direction
47:35
as the spacecraft transitioned between domains. The fact that it
47:40
didn't indicate something fundamental about the interaction between solar and
47:47
interstellar magnetic fields that current physics doesn't explain. Scientists must
47:54
come to some understanding of why the magnetic field doesn't change.
48:00
That process remains simply not understood. He The parallel alignment
48:06
suggests the two fields are somehow coupled or influenced by
48:12
structures operating on scales larger than the heliosphere itself. Perhaps
48:18
the local interstellar clouds magnetic field naturally aligns with our
48:24
Sun's field due to their mutual motion through the galaxy.
48:29
Perhaps magnetic reconnection events at the heliopause create channels that
48:34
enforce alignment. Perhaps the physics of magnetic field interactions at
48:40
this boundary differs from anything we've modeled. Nobody knows yet.
48:46
The magnetic field measurements revealed another peculiarity near the termination
48:52
shop the Sun rotates every twenty six days, which causes
48:57
the interplanetary magnetic field to alternate direction every thirteen days.
49:03
This alternating pattern creates a structure like zebra stripes moving
49:10
outward with the solar wind. Before reaching the termination shock,
49:16
these stripes moved past Voyager at predictable intervals. After crossing
49:22
the shock, the pattern changed dramatically. The stripe started moving
49:27
at nearly the same speed as Voyager itself, Stretched and
49:32
distorted by the shock's effects. It took more than one
49:36
hundred days for a single stripe to pass the spacecraft
49:40
and for the magnetic field to switch directions. The stretching
49:45
indicated the termination shock wasn't just slowing the solar wind.
49:51
It was fundamentally altering how the Sun's magnetic field propagated
49:57
through space. Then came twenty twenty. Voyager one's magnetometer registered
50:05
an abrupt jump in the intensity of magnetic fields embedded
50:09
in the interstellar plasma. Simultaneously, the plasma detector measured a
50:15
rise in plasma density. The jumps appeared transient at first,
50:20
temporary fluctuations that would fade. They didn't fade. The anomalies
50:26
persisted through twenty twenty twenty twenty one and beyond. Researchers
50:33
initially attributed the changes to surges of solar plasma smashing
50:38
against the heliosphere's boundary, creating swells that reverberated through interstellar space.
50:46
Solar activity can compress interstellar plasmas and intensify their magnetic
50:52
fields even at distances of one hundred twenty astronomical units,
50:58
but the anomalies did and debate. The magnetic field intensity
51:04
remained elevated, the plasma density stayed high. Some mission scientists
51:10
began questioning whether these effects originated with the.
51:14
Speaker 2: Sun at all.
51:16
Speaker 1: Perhaps Voyager had entered a new type of interstellar structure.
51:22
Perhaps the very local interstellar medium contained regions of enhanced
51:28
density and magnetic field strength that weren't connected to solar activity.
51:34
The mystery remains unresolved. Voyager continues transmitting data, and that
51:40
data continues revealing patterns nobody anticipated. The spacecraft are exploring
51:47
genuinely unknown territory, encountering phenomena that challenge existing models of
51:55
how interstellar space operates. The heliosphere itself responds to the
52:03
eleven year solar activity cycle. The heliopause isn't static. It
52:09
breeds like a lung, expanding and contracting as solar output varies.
52:15
During solar maximum, when the Sun's activity peaks, the solar
52:20
wind blows harder and pushes the heliopause farther out. During
52:25
solar minimum, when the sun quiets, the boundary contracts inward.
52:31
This dynamic behaviour means future spacecraft crossing the heliopause might
52:37
encounter it at different distances depending on when they arrive.
52:43
The boundary isn't a fixed landmark in space. It's a
52:47
moving target, responsive to both solar cycles and variations in
52:52
the interstellar medium pressing against it from the outside. Voyager
52:57
one crossed during solar maximum at one hundred and twenty
53:01
one point six astronomical units. Voyager two crossed during solar
53:08
minimum at one hundred nineteen astronomical units. The distances were
53:14
nearly identical, despite vastly different solar conditions. This consistency struck
53:21
scientists as very strange. It suggested the heliopause's position might
53:28
be more strongly influenced by interstellar pressure than by solar
53:33
wind strength. The two crossings also revealed differences in the
53:37
boundary's character. Voyager one observed solar wind speeds dropping nearly
53:43
to zero close to the heliopause. Voyager two measured relatively
53:49
high solar wind speeds almost all the way through until crossing.
53:55
Voyager two's data suggested a smoother, thinner heliopause than Voyager
54:03
one encountered. Both spacecraft apparently traverse the boundary in less
54:09
than a day. Crossing didn't take weeks or months. It
54:13
happened fast, reinforcing the idea that the heliopause is sharp
54:19
rather than gradual, at least on scales relevant to spacecraft motion.
54:25
The differences between the two crossings illuminate how location and
54:30
timing affect what spacecraft observe. The heliosphere isn't symmetric. Its
54:37
shape gets compressed and distorted by the interstellar medium's pressure
54:42
and magnetic fields. Voyager one exited near the nose the
54:47
front of the heliosphere relative to our motion through the galaxy.
54:53
Voyager two exited closer to the flank. These different exit
54:58
points sample different regions of the boundary, revealing variations in thickness, permeability,
55:07
particle flow, and magnetic field behavior. The heliosphere has texture
55:14
structure regions, where the boundary behaves differently depending on local conditions.
55:21
The plasma environments on either side of the heliopause differ fundamentally.
55:27
Inside the plasma is hot and sparse, heated by the
55:31
Sun and blown outward at high speed. Outside, the plasma
55:36
is cold and dense, part of the ancient interstellar cloud
55:40
through which our solar system happens to be traveling hot
55:44
but sparse versus cold but dense. The difference defines the boundary.
55:51
The temperature contrast creates the zones of extraordinary heat near
55:56
the heliopause, where particles become trapped and compressed. The density
56:02
contrast creates the sharp transition that voyagers instruments detected. The
56:09
magnetic field differences, or lack thereof, create the ongoing mystery
56:16
that scientists are still working to explain. Understanding these plasma
56:23
properties matters beyond just characterizing our local cosmic neighborhood. Every
56:30
star in the galaxy creates its own heliosphere, a bubble
56:35
carved out of the interstellar medium by stellar wind. Studying
56:41
how our Sun's bubble interacts with surrounding space provides insights
56:47
into stellar physics throughout the universe. The measurements Voyager continues
56:53
sending back help scientists model not just our heliosphere, but
56:58
heliospheres around us the stars. They reveal universal principles about
57:04
how stellar winds interact with interstellar matter, how magnetic fields
57:09
behave a boundaries, how cosmic rays propagate through different environments,
57:15
and Voyager keeps going. Both spacecraft continue deeper into interstellar
57:22
space at roughly three astronomical units per year. Voyager one
57:28
now travels at one hundred seventy two astronomical units from Earth,
57:35
the most distant human made object in existence. Voyager two
57:40
follows at one hundred and forty three astronomical units. The
57:45
spacecraft will eventually run out of power. The plutonium that
57:50
fuels their radio isotope thermoelectric generators decay, steadily producing less
57:58
electricity each year. Mission controllers have been shutting down non
58:03
essential systems to conserve power. The heaters keeping instruments warm
58:09
get turned off, redundant systems get disabled. By the mid
58:14
two thousands, both Voyagers would lightly go silent. Their transmitters
58:20
will fail, their instruments will freeze. They'll become inert artifacts
58:28
drifting through the galaxy carrying golden records intended for civilizations
58:35
that might find them millions of years from now. But
58:39
for now they're still active, still transmitting, still revealing what
58:44
exists beyond the edge of everything humans had previously explored.
58:50
The data coming back from interstellar space revealed something nobody anticipated.
58:57
In twenty twenty, Voyager one's magnet autometer registered an abrupt
59:02
jump in magnetic field intensity. The plasma detector simultaneously measured
59:08
rising plasma density. Researchers initially assumed these spikes came from
59:14
solar eruptions, plasma surges from the Sun smashing against the
59:19
heliosphere's boundary, creating reverberations that compressed interstellar plasma and intensified
59:29
magnetic fields, temporary disturbances that would fade, But the anomalies
59:36
didn't stop.
59:38
Speaker 2: They continued. Month after month.
59:41
Speaker 1: The measurements showed persistent changes that didn't match patterns from
59:46
solar activity. Scientists started questioning whether these signals originated with
59:53
the Sun at all. Maybe Voyager was detecting something else, entirely,
1:00:00
a structure in interstellar space itself, some feature of the
1:00:05
local interstellar medium that previous models hadn't predicted. The very
1:00:12
local interstellar Medium abbreviated v LISM turned out to be
1:00:19
more complex than expected before crossing the heliopause, scientists imagined
1:00:24
interstellar space as relatively uniform empty, quiet avoid between stars,
1:00:31
where plasma drifted slowly and magnetic fields barely fluctuated. Voyager's
1:00:37
instruments painted a different picture. The vlism has texture, structure,
1:00:44
variations in density that change over surprisingly short distances. The
1:00:50
plasma isn't uniformly distributed, but forms gradients regions where particles
1:00:58
concentrate more densely than surrounding areas. In October twenty twenty,
1:01:04
astronomers reported significant unexpected increases in density detected by both voyagers.
1:01:12
The measurements implied that the density gradient is a large
1:01:16
scale feature of the vlism in the general direction of
1:01:21
the heliospheric nose the front of the heliosphere relative to
1:01:26
our motion through the galaxy. As voyager continues outward, it's
1:01:32
traveling through a region where the local interstellar medium is
1:01:36
being compressed or is naturally denser than previously expected. This
1:01:43
has implications for understanding the structure of the local interstellar
1:01:50
cloud through which our solar system happens to be moving.
1:01:55
Our solar system isn't stationary. It moves through the galaxy
1:02:00
at roughly twenty six kilometers per second relative to nearby stars.
1:02:07
That motion carries us through different regions of interstellar space,
1:02:12
clouds of gas and dust with varying properties. Currently, we're
1:02:17
passing through what's called the local interstellar cloud, sometimes referred
1:02:23
to as the local fluff. It's a region of slightly
1:02:27
higher density than average interstellar space, with temperatures around six
1:02:33
thousand kelvin and particle densities of about zero point three
1:02:39
atoms per cubic centimeter. That's still incredibly empty by Earth standards,
1:02:46
a better vacuum than anything achievable in laboratories, but it's
1:02:52
denser than the average between star environment. The local interstellar
1:02:57
cloud itself sits inside a larger structure called the local bubble,
1:03:03
a region hundreds of light years across where ancient supernova
1:03:07
explosions swept away most of the gas, leaving a cavity
1:03:12
of extremely low density space. Our Solar system is near
1:03:17
one edge of this bubble, moving through one of the
1:03:22
denser clouds within it. Voyager's measurements help map these structures,
1:03:29
revealing details about the interstellar environment that surrounds our cosmic neighborhood.
1:03:37
One of the most surprising findings from the VLSM involves
1:03:42
plasma waves. Voyager one's plasma wave instrument, those two bunny
1:03:48
ear antennas extending ten meters behind the spacecraft detected sporadic
1:03:54
bursts of plasma oscillations for years, brief whistles when solar
1:03:59
eruptions and sent shock waves rippling through interstellar space, making
1:04:04
the plasma ring like a struck bell. But in the
1:04:09
sparse collection of atoms filling interstellar space, Voyager eventually started
1:04:16
detecting something different, long lasting series of waves where it
1:04:21
previously only detected occasional bursts, continuous emissions that provided an
1:04:28
ongoing measure of plasma density. These waves vibrate electrons back
1:04:34
and forth along magnetic field lines. The electrons ring out
1:04:39
a characteristic frequencies, depending on how closely packed they are.
1:04:44
Higher pitch means higher density. Six months after the first
1:04:50
continuous detection, another whistle appeared, louder and even higher pitched.
1:04:57
The interstellar medium appeared to be getting thicker quickly. The
1:05:03
discovery of these persistent plasma waves was unexpected. Scientists hadn't
1:05:09
predicted continuous emissions. The finding provides valuable data about the
1:05:15
structure and properties of the very local interstellar medium as
1:05:21
Voyager travels through it. The plasma density Voyager measures in
1:05:26
interstellar space is about zero point zero eight particles per
1:05:31
cubic centimeter, roughly eighty times denser than the heliosphere's interior.
1:05:38
That jump in density defines the heliopores, but the density
1:05:43
isn't constant. It varies, sometimes gradually, sometimes abruptly. The variation
1:05:50
suggest that interstellar space has a complex structure, with regions
1:05:54
of different particle concentration. Voyager is essentially taken a sample
1:06:00
through the vlism, measuring properties along a single line as
1:06:08
it moves outward. Each measurement reveals details about the environment
1:06:15
at that specific location. Scientists can extrapolate from Voyager's trajectory
1:06:21
to make educated guesses about surrounding regions, but there's no
1:06:26
way to know for certain what exists a few astronomical
1:06:30
units to the side of Voyager's path. Without sending another spacecraft,
1:06:36
the VLISM remains mostly unmapped. Two data points, Voyager one
1:06:43
and Voyager two, traveling through an ocean of space, sending
1:06:48
back measurements from wherever they happen to be. It's like
1:06:52
trying to understand Earth's entire ocean by taking samples from
1:06:57
two ships sailing in roughly the same direction, separated by
1:07:03
several hundred miles. Still, those two ships have revealed fundamental
1:07:09
truths about the ocean they're crossing. The magnetic field measurements
1:07:15
proved particularly illuminating. Both voyagers confirmed a result that contradicted
1:07:22
theoretical predictions. The magnetic field in the region just beyond
1:07:28
the heliopause runs parallel to the magnetic field inside the heliosphere.
1:07:34
Scientists expected significant differences in field direction. Models suggested the
1:07:41
interstellar magnetic field should be oriented differently from the solar
1:07:46
magnetic field, creating a rotation or twist at the boundary.
1:07:51
Neither voyager detected that rotation. The fields aligned. Scientists don't
1:07:58
understand why the process that produces this alignment remains unexplained.
1:08:05
Magnetic Fields in space form when charged particles move through plasma.
1:08:11
The Sun's rotation and the outward flow of solar wind
1:08:16
create the heliosphere's magnetic field, which gets dragged along by
1:08:20
the solar wind like a garden hose whipping around as
1:08:25
water flows through it. The interstellar magnetic field comes from
1:08:30
different sources, galactic rotation, ancient supernova remnants, the motion of
1:08:36
gas clouds through the galaxy. These fields should be independent, unrelated,
1:08:43
yet at the boundary they somehow line up. The alignment
1:08:48
suggests some physical mechanism at the heliopause causes the fields
1:08:52
to couple or synchronize, or maybe the interstellar magnetic field
1:08:58
in this particular region of space happens to be oriented
1:09:02
similarly to the heliospheric field by coincidence. Neither explanation is
1:09:09
entirely satisfying. The mystery highlights how much remains unknown about
1:09:16
magnetic field behavior in space plasmas. Laboratory experiments can't replicate
1:09:22
the conditions at the heliopause, the enormous scales, the incredibly
1:09:28
low densities, the weak magnetic fields. Computer simulations help, but
1:09:33
require assumptions about plasma physics that might not hold true
1:09:38
in all environments. Voyager's measurements provide ground truth, real data
1:09:44
from the actual boundary, and that data reveals gaps in
1:09:49
our understanding. Cosmic rays present another puzzle. High energy particles
1:09:57
accelerated by supernova I explosions and other violent galactic events.
1:10:05
Before voyage A crossed the heliopause, scientists predicted cosmic ray
1:10:10
intensity would reach maximum at the termination shock the boundary
1:10:15
where solar wind slows abruptly. Theoretical models suggested interstellar ions
1:10:23
would bounce back and forth across the shock, gaining energy
1:10:27
with each bounce, until they became high speed cosmic rays.
1:10:32
The shock should be where cosmic rays concentrate most intensely,
1:10:38
but Voyager one found the opposite. Cosmic ray intensity didn't
1:10:43
peak at the shock, it kept increasing As a voyager
1:10:48
moved farther beyond the shock, the intensity continued rising through
1:10:54
the helio sheath and into interstellar space. This pattern suggests
1:11:01
the source of cosmic rays lies in a region scientists
1:11:06
hadn't predicted. Somewhere beyond the heliopause in interstellar space itself,
1:11:12
cosmic rays are being accelerated or concentrated. Maybe the heliopause
1:11:19
acts as a kind of cosmic ray filter, allowing only
1:11:23
the highest energy particles to pass inward while reflecting lower
1:11:29
energy ones bag into interstellar space. Or maybe there's a
1:11:34
region just beyond the heliopause where magnetic field interactions accelerate particles.
1:11:41
The measurements from both voyagers show cosmic ray intensity is
1:11:47
about ninety percent of what's detected farther out when they're
1:11:52
just beyond the boundary, then increases to full interstellar levels.
1:11:59
Within a f few astronomical units, a boundary layer exists
1:12:06
where cosmic ray intensity transitions from heliospheric to fully interstellar values.
1:12:15
Understanding cosmic ray behaviour matters for more than academic curiosity.
1:12:21
Cosmic rays pose radiation hazards to spacecraft and astronauts. They
1:12:27
can damage electronics, degrade solar panels, and increase cancer risk
1:12:32
for humans in space. Knowing how cosmic rays propagate through
1:12:37
different environments helps mission planners design better shielding and assess
1:12:44
radiation exposure for future deep space missions. Voyager's measurements revealed
1:12:51
that the heliosphere shields Earth and other planets from more
1:12:56
than seventy percent of galactic cosmic gradiation. Without that protection,
1:13:03
life on Earth would face significantly higher radiation levels. The
1:13:07
heliosphere functions as a magnetic bubble that deflects or slows
1:13:13
cosmic rays before they reach the inner solar system. Lower
1:13:18
energy cosmic rays get deflected entirely. Higher energy ones penetrate,
1:13:24
but lose energy as they fight through the outward flowing
1:13:28
solar wind and tangled magnetic fields. Only the most energetic
1:13:33
cosmic rays make it all the way to Earth's orbit
1:13:37
without significant energy loss. This filtering effect changes with solar activity.
1:13:44
During solar maximum, when the Sun's magnetic field is strongest
1:13:48
and most complex, cosmic ray intensity and Earth decreases. During
1:13:55
solar minimum, more cosmic rays penetrate to the inner Solar system.
1:13:59
The eleven year solar cycle creates corresponding variations in cosmic
1:14:04
ray exposure. Voyager's journey beyond the heliosphere also revealed details
1:14:11
about the heliosphere's shape. Early models assumed a roughly spherical bubble,
1:14:18
the termination shock and heliopause would form concentric shells around
1:14:23
the Sun, symmetric in all directions. Voyager's measurements showed that
1:14:28
assumption was wrong. The heliosphere is asymmetric, compressed distorted by
1:14:36
external pressure from the interstellar medium and by magnetic fields
1:14:41
draped around it. The overall shape resembles a comet more
1:14:47
than the sphere, roughly rounded on one side, with a
1:14:52
long tail extending in the opposite direction. The tail, called
1:14:58
the heliotail, stretch for thousands of astronomical units downstream from
1:15:03
the Sun's motion through the galaxy, solar wind that flows
1:15:08
out the backside of the heliosphere gets swept into this tail,
1:15:13
creating an elongated structure that trails behind like a cosmic contrail.
1:15:19
The heliotail has never been directly observed. No spacecraft has
1:15:24
traveled in that direction, but models based on Voyager's measurements
1:15:30
and observations from the Interstellar Boundary Explorer satellite suggests it exists.
1:15:37
Mapping its structure remains a goal for future missions. The
1:15:42
heliospheres asymmetry explains why Voyager one and Voyager two cross
1:15:49
the termination shock at different distances ninety four astronomical units
1:15:55
for Voyager one, eighty three point seven for Voyager two.
1:16:00
The boundary isn't spherical, It's closer to the Sun in
1:16:04
some directions than others. The interstellar magnetic field tilts relative
1:16:10
to the direction of the interstellar flow, creating pressure that
1:16:15
pushes the southern hemisphere of the heliosphere inward. The termination
1:16:22
shock forms an offset sphere pushed back in the direction
1:16:27
we're moving through the galaxy closer in other directions. With
1:16:33
the whole structure tilted and compressed. The heliosphere also breathes.
1:16:40
Its size changes in response to solar activity. During solar maximum,
1:16:45
increased solar wind pressure pushes the heliopause outward. During solar minimum,
1:16:52
reduced pressure allows the heliopause to contract. The boundary moves
1:16:57
in and out like a lung, expanding and contracting with breath.
1:17:02
This dynamic behavior means future spacecraft crossing the heliopause might
1:17:08
encounter it at different distances depending on where the Sun
1:17:12
is in its activity cycle. The heliopause isn't a fixed boundary,
1:17:19
but a moving interface that responds to changing conditions on
1:17:24
both sides. Voyager's measurements quantified how much the heliopause can move.
1:17:31
The difference between solar maximum and minimum can shift the
1:17:36
boundary by ten to twenty astronomical units billions of kilometers.
1:17:42
That's significant. The spacecraft approaching the heliopause might find it
1:17:48
farther away than expected if the Sun's activity has increased
1:17:54
since mission planning began, or closer if activity has decreased.
1:18:00
Understanding this variability helps scientists' interpret measurements and predict where
1:18:08
future spacecraft will encounter the boundary. And what about the
1:18:13
bow shock? Early models predicted the Sun's motion through the
1:18:18
interstellar medium would create a bow shock ahead of the heliosphere,
1:18:24
similar to the shockwave that forms in front of a
1:18:27
ship moving through water. The Interstellar Boundary Explorer satellite and
1:18:35
Voyager data revealed something unexpected. There's no booshock. The interstellar
1:18:42
medium flows past the heliosphere without forming that predicted shockwave.
1:18:48
This absence indicates the interstellar medium is moving subsonically relative
1:18:54
to the Sun, slower than the speed of sound.
1:18:57
Speaker 2: In that medium.
1:18:59
Speaker 1: Without suit personic relative motion, no bowshock forms. The missing
1:19:04
bowshock changed scientific understanding of how the heliosphere interacts with
1:19:11
its surroundings. Instead of a sharp shock wave, there's a
1:19:16
gentler transition region, sometimes called the hydrogen wall, a region
1:19:22
where neutral hydrogen from the interstellar medium piles up as
1:19:27
it encounters the heliosphere's edge. Voyager spacecraft first detected this
1:19:33
structure in nineteen ninety two. New horizons confirmed the detection
1:19:39
in twenty eighteen. The hydrogen wall isn't as dramatic as
1:19:44
a bowshock would be, but it represents an important boundary
1:19:49
feature that affects how neutral atoms behave as they approach
1:19:55
the heliosphere. Voyager continues revealing surprises about interstellar space. The
1:20:02
spacecraft aren't done teaching us yet. The two Voyager spacecraft
1:20:08
cross the heliopause at nearly identical distances one hundred twenty
1:20:13
one astronomical units for Voyager one, one hundred nineteen for
1:20:18
Voyager two. That similarity seems reasonable until you consider the timing.
1:20:24
Voyager one crossed during solar maximum, when the Sun's activity peaks,
1:20:30
Voyager two crossed during solar minimum, when activity drops to
1:20:35
its lowest point. The heliopause should have been farther out
1:20:41
during maximum closer during minimum, but both spacecraft encountered it
1:20:48
at essentially the same distance. Scientists call this consistency very strange.
1:20:56
The crossings themselves differed in character. Voyager one measured solar
1:21:01
wind speeds dropping nearly to zero as it approached the boundary.
1:21:07
The wind slowed, stalled, almost stopped, then the spacecraft crossed over.
1:21:13
Voyager two measured relatively high wind speeds almost until the
1:21:18
moment of crossing. No gradual slowed down, no stalling zone,
1:21:24
just steady flow. Then transition the boundary itself appeared smoother
1:21:30
and thinner for Voyager two. Voyager one's crossing involved more turbulence,
1:21:36
more back and forth fluctuations. Both spacecraft traversed the heliopause
1:21:41
in less than a day, but the experience wasn't identical.
1:21:46
Location matters. Voyager one exited near the front of the heliosphere,
1:21:52
the direction the Solar System moves through the galaxy. That's
1:21:57
where the interstellar wind hit head on. Voyager two crossed
1:22:02
closer to the flank, off to the side. The heliopause
1:22:07
behaves differently in different locations. It's not uniform, not consistent.
1:22:14
The boundary's properties change depending on where you cross it,
1:22:18
when you cross it, what the Sun's doing at that moment.
1:22:23
Both spacecraft detected something unexpected at the heliopause, particle leakage.
1:22:29
Speaker 2: The boundary isn't sealed. It's porous.
1:22:33
Speaker 1: Particles from inside the heliosphere slip through into interstellar space.
1:22:39
Particles from outside find their way in. Voyager one detected
1:22:44
interstellar particles twice before crossing. Brief intrusions scientists attributed to
1:22:51
interstellar flux tubes, channels, or pathways, allowing material to penetrate
1:22:58
the boundary. The hull leagues not catastrophically, but measurably. Voyager
1:23:05
two's location near the flank showed even more porosity. That
1:23:10
region appears more permeable than where Voyager one crossed. The
1:23:15
heliopause isn't a solid wall. It's more like a membrane,
1:23:20
flexible semi permeable, with varying thickness and permeability depending on location.
1:23:29
Some regions seal tightly, others let particles drift across. This
1:23:36
challenges the simple picture of a clean boundary separating two domains.
1:23:43
The plasma environment on either side tells its own story.
1:23:47
Inside the heliosphere, plasma is hot and sparse, heated by
1:23:52
the Sun, spread thin by the solar wind's expansion. Outside,
1:23:57
in interstellar space, plasma is colder but denser. The temperature
1:24:02
drops the density rises. That density jump provided crucial evidence
1:24:08
for Voyager's crossing. Voyager one's plasma wave instrument detected electron
1:24:14
plasma oscillations resonating a two point six killer hertz, a
1:24:20
frequency corresponding to electron density about eighty times higher than
1:24:25
inside the heliosphere. That's the signature scientists needed proof of
1:24:31
interstellar space. The measurement came with a twist. Voyager one's
1:24:37
direct plasma instrument failed in nineteen eighty decades before reaching
1:24:44
the heliopause. Engineers couldn't directly measure plasma properties. They needed
1:24:51
indirect methods. The plasma wave instrument became the solution. When
1:24:57
solar eruptions sent shock waves through interstellar plasma, that plasma
1:25:03
rang like a struck bell, vibrating at its natural frequency.
1:25:09
The spacecraft listened to those vibrations. The frequency revealed the
1:25:15
density problem solved through ingenuity. Six months after the first detection,
1:25:22
another whistle appeared, louder, higher pitched. The interstellar medium was
1:25:28
getting thicker quickly. Voyager one discovered something else, continuous plasma
1:25:36
wave emissions. Before crossing the instrument detected only sporadic bursts.
1:25:42
After crossing, it measured long lasting waves reverberating through space.
1:25:48
The electrons vibrated back and forth along magnetic field lines,
1:25:54
creating oscillations that provided ongoing density measurements. Scientists could map
1:26:02
variations in the local interstellar medium as Voyager traveled through it.
1:26:09
Those variations matter. In October twenty twenty, both Voyager spacecraft
1:26:15
detected a significant unexpected increase in density the very local
1:26:21
interstellar medium. The region immediately beyond the heliopause showed a
1:26:27
density gradient, a large scale feature in the direction the
1:26:32
heliosphere's nose points. The interstellar medium isn't uniform either, It
1:26:39
has structure regions of higher and lower density variations that
1:26:47
affect how the heliosphere interacts with its surroundings. The temperature
1:26:53
dynamics at the boundary proved equally surprising. Scientists expected a smooth,
1:26:59
gradual transition, cool solar wind meeting cool interstellar plasma. Instead,
1:27:07
Voyager found extreme temperatures thirty thousand to fifty thousand kelvin
1:27:12
in some regions. The boundary creates zones of extraordinary heat,
1:27:17
where charged particles become trapped and compressed. Other nearby regions
1:27:23
stay relatively cooler. It's a patchwork hot and cold plasma
1:27:29
mixed together in patterns unlike anything inside the heliosphere. This
1:27:35
earned the nickname Wall of Fire, not because spacecraft burn
1:27:40
up the particle density is too low to transfer heat,
1:27:45
but because of the temperature extremes. Researchers expected gradual fading
1:27:51
between solar and interstellar environments. Voyager found abrupt shifts, almost
1:27:59
like stepping over a threshold one side then the other.
1:28:04
The transition isn't gentle. As spacecraft approached the boundary, instruments
1:28:09
recorded sudden changes in particle density and magnetic fields, signatures
1:28:16
of turbulence. The region is more chaotic than models predicted.
1:28:22
The heliopause isn't a calm interface. It's dynamic, fluctuating, responding
1:28:31
to pressure from both sides. And then there's the magnetic
1:28:35
field mystery. Before Voyager I crossed, scientists expected significant differences
1:28:43
between the heliospheric magnetic field and the interstellar field. Different directions,
1:28:50
different orientations. That's what models predicted, that's what made sense
1:28:56
based on observations from other missions. Huge one found something different.
1:29:03
The interstellar magnetic field aligned largely parallel to the heliospheric field,
1:29:09
same direction, similar orientation. That was unexpected, maybe an anomaly
1:29:16
specific to where Voyager one crossed. Then Voyager two confirmed it.
1:29:21
The same alignment, the same parallel orientation, not an anomaly,
1:29:26
a real feature. Scientists must understand why the magnetic field
1:29:31
doesn't change direction at the heliopause. The process isn't understood,
1:29:38
the physics remains unclear. Two independent measurements from two different
1:29:44
locations at two different times show the same thing. The
1:29:49
interstellar magnetic field and the heliospheric field align somehow, for
1:29:56
reasons still being investigated. This discovery contradicted predictions based on
1:30:03
theoretical models and observations from missions like ibex. It suggests
1:30:11
the interaction between solar and interstellar magnetic fields is more
1:30:17
complex than current understanding. The fields don't simply meet at
1:30:22
the boundary and transition they connect, they align. They interact
1:30:28
in ways that preserve directional continuity across the heliopores. Understanding
1:30:35
this matters beyond just satisfying curiosity. Magnetic fields govern how
1:30:41
particles move, how energy transfers, how the heliosphere shields Earth
1:30:46
from galactic cosmic rays. If the fields align unexpectedly, that
1:30:52
changes how protection works. It changes predictions about space weather.
1:30:57
It changes models of how steellar winds interact with interstellar environments,
1:31:05
not just for our Sun, but for other stars throughout
1:31:09
the galaxy. Voyager continues measuring magnetic field properties in interstellar space.
1:31:16
The spacecraft traveled deeper into the very local interstellar medium,
1:31:21
sending back data about field strength, direction fluctuations. In twenty twenty,
1:31:29
Voyager one's magnetometer registered abrupt jumps in field intensity. The
1:31:35
plasma detector measured simultaneous rises in plasma density. These transient
1:31:42
jumps appeared to originate from surges of solar plasma smashing
1:31:47
against the heliosphere's boundary, creating swells that reverberate through interstellar space,
1:31:55
compressing interstellar plasma, intensifying magnetic fields. But the anomalies didn't debate,
1:32:04
They continued persisted. Some mission scientists began questioning whether these
1:32:11
changes originated with the Sun at all. Maybe they represent
1:32:16
something else, a new type of interstellar structure, a region
1:32:21
of naturally higher density or stronger fields. The mystery remains open.
1:32:28
Voyager one discovered interstellar space is quiet. Magnetic fluctuation intensity
1:32:35
is very small beyond the heliopause. Inside the heliosphere, the
1:32:39
magnetic field constantly varies, responding to solar activity, solar wind turbulence,
1:32:46
the rotating Sun's changing output. Outside fluctuations diminish, the field
1:32:54
is more stable, more consistent. The interstellar environment doesn't experience
1:33:00
the same constant stirring from stellar winds. That quietness contrasts
1:33:06
with the boundaries violence. At the heliopause itself, conditions are turbulent, chaotic, extreme,
1:33:15
But once you move away from that interface into true
1:33:18
interstellar space, things calm. The environment stabilizes. It's not that
1:33:25
interstellar space is empty or inactive. It has its own dynamics,
1:33:30
its own variations, but it operates at a different rhythm
1:33:34
than the heliosphere's constant solar driven churn. The cosmic ray
1:33:40
environment tells another story. Inside the heliosphere, low energy particles dominate,
1:33:47
mostly originating from the Sun. Galactic cosmic rays. High energy
1:33:52
particles accelerated by supernovae and other violent galactic events are present,
1:33:58
but suppressed. The heliosphere blocks them, deflects them, reduces their intensity.
1:34:06
At the heliopause, that changes dramatically. Voyager one recorded a
1:34:12
one thousandfold drop in solar particles simultaneous with a nine
1:34:16
percent increase in galactic cosmic rays. The shift happened over days.
1:34:23
The solar particles disappeared, the cosmic rays surged. Voyager one
1:34:29
discovered the heliosphere protects Earth and other planets from more
1:34:35
than seventy percent of galactic radiation. Without that shield, surface
1:34:41
conditions on Earth would be harsher life would face greater
1:34:46
radiation exposure. Voyager two found a boundary layer just beyond
1:34:51
the heliopause, a region where low energy particles streamed outward
1:34:57
along magnetic field lines and cosmic ray intensities reached only
1:35:02
ninety percent of levels farther out. Another transition zone, another
1:35:08
layer of complexity at the boundary. The crossing isn't instantaneous
1:35:14
in every respect. Some properties change abruptly, others transition more gradually.
1:35:22
The cosmic ray spectra Voyager measured provide detailed information about
1:35:27
particle energies. Hydrogen and helium spectra show broad peaks from
1:35:33
ten to forty million electron vaults per nucleon. The distribution
1:35:39
of energies reveals how cosmic rays are accelerated throughout the
1:35:43
galaxy and how they propagate through space. These measurements help
1:35:49
scientists understand not just the local environment, but galactic scale processes.
1:35:56
One puzzle remains from the termination shock crossing. Years earlier,
1:36:01
scientists predicted cosmic ray ions would reach maximum intensity at
1:36:07
the shock, bouncing back and forth, gaining energy with each bounce,
1:36:13
becoming high speed particles.
1:36:15
Speaker 2: But Voyager one didn't find that maximum at the shock.
1:36:19
Speaker 1: Instead, cosmic ray intensity continued increasing as the spacecraft moved
1:36:25
farther beyond the shock through the helio sheath toward the heliopause.
1:36:31
The source of those cosmic rays is somewhere else, a
1:36:35
region yet to be identified, a process still not fully understood.
1:36:41
The termination shock itself surprise researchers in multiple ways. Scientists
1:36:47
expected solar wind speed would drop to a few hundred
1:36:51
thousand miles per hour beyond the shock, Voyager found much
1:36:57
lower speeds. Sometimes the wind appeared to flow backward toward
1:37:03
the Sun, the first time instruments detected wind blowing back
1:37:08
at the spacecraft, completely unexpected behavior. The magnetic field's zebra
1:37:17
stripe pattern alternating field directions carried outward by solar wind
1:37:25
changed beyond the shock. As the Sun rotates every twenty
1:37:29
six days, the field alternates every thirteen days. Inside the
1:37:35
termination shock, those stripes move rapidly past the spacecraft. Beyond
1:37:41
the shock, the stripe slowed dramatically. It took more than
1:37:46
one hundred days for one stripe to pass Voyager. The
1:37:50
pattern moved at nearly the spacecraft's speed, almost synchronized. That
1:37:56
wasn't predicted either. These discoveries forced scientists to rethink models
1:38:03
of the heliosphere. The boundary regions, termination shock helio sheath
1:38:09
heliopores behave differently than expected. They're more complex, more variable,
1:38:16
more surprising than decades of theoretical work suggested. Direct measurements
1:38:22
revealed reality doesn't match simplified models, and Voyager keeps going.
1:38:29
Both spacecraft continue operating, continue transmitting, continue revealing properties of
1:38:36
interstellar space. As of February twenty twenty six, Voyager one
1:38:42
is one hundred seventy two point one two astronomical units
1:38:47
from Earth. Voyager two is at one hundred forty three
1:38:51
point zero five astronomical units. They're the most distant human
1:38:56
made objects ever created, still function, still sending data across
1:39:02
billions of kilometers of space. Their continued operation depends on
1:39:08
failing power systems and aging components, but for now they
1:39:13
persist measuring magnetic fields, detecting cosmic rays, monitoring plasma density,
1:39:20
mapping the very local interstellar medium. Every transmission adds another
1:39:26
piece to humanity's understanding of the space beyond the Sun's influence,
1:39:34
the space where our solar system ends and the galaxy
1:39:39
truly begins. The hydrogen wall represents another unexpected structure at
1:39:46
the heliosphere's edge. Voyager first detected it in nineteen ninety two,
1:39:52
a region where neutral hydrogen from interstellar space piles up
1:39:57
as it encounters the heliosphere. Not charged particles affected by
1:40:03
magnetic fields, but neutral atoms responding to different forces. The
1:40:09
wall forms where interstellar hydrogen gets slowed and compressed by
1:40:14
interaction with the heliosphere's boundary. Like water piling up against
1:40:20
the dam, the density increases the atoms accumulate, creating a
1:40:26
detectable structure that New Horizon spacecraft confirmed again in twenty eighteen,
1:40:35
twenty six years after initial detection. Same feature still there,
1:40:44
still marking the transition zone where solar and interstellar material meat.
1:40:51
Scientists predicted this wall would be hot hydrogen temperatures elevated
1:40:57
by compression and interaction. The observations confirmed the prediction, but
1:41:03
the exact physics remains complex. How neutral atoms behave at
1:41:08
this boundary differs from charged particle behavior. They respond to
1:41:14
different forces, follow different paths, create different structures. The hydrogen
1:41:21
wall provides crucial information about that neutral component of the
1:41:27
interstellar medium, something voyagers charged particle instruments couldn't fully measure,
1:41:36
a complementary piece of the boundary puzzle. Meanwhile, scientists expected
1:41:44
something else entirely that voyager never found. A bow shock
1:41:51
picture a boat moving through water. The bow creates a
1:41:56
shock wave ahead of the boat, a visible vs shape
1:42:00
spreading outward. For decades, scientists assumed our solar system's motion
1:42:09
through the interstellar medium would create something similar a bow shock,
1:42:15
forming a head of the heliosphere where our bubble pushes
1:42:18
through interstellar space. Theoretical models included it. Diagrams showed it.
1:42:26
Everyone expected Voyager would detect it before reaching the heliopause.
1:42:31
Voyager found nothing, no bow shock. The expected structure wasn't there.
1:42:38
Data from NASA's Interstellar Boundary Explorer spacecraft confirmed the absence
1:42:44
in twenty twelve. Combined with Voyager observations, the conclusion became clear.
1:42:51
The heliosphere has no bow shock, at least not in
1:42:55
the traditional sense. This absence forced scientists to reconsider fundamental
1:43:03
assumptions about the Solar System's motion through the galaxy. If
1:43:09
the local interstellar medium were supersonic, moving faster than sound
1:43:14
speed in that medium, a bow shock would definitely form
1:43:18
the physics demands it. But recent data suggests the interstellar
1:43:23
flow is subsonic instead, moving slower than expected. That changes everything.
1:43:31
No supersonic flow means no bowshock. The heliosphere doesn't crash
1:43:36
through the interstellar medium like a speedboat through water. It
1:43:40
drifts more gently. The interaction is calmer, the boundary forms differently,
1:43:48
or perhaps the physics at this boundary differs from simple
1:43:52
models entirely, maybe fact as scientists haven't fully considered affect
1:43:57
how the interaction plays out. Either way, the missing bowshock
1:44:02
represents another surprise, another assumption overturned by direct observation. Reality
1:44:12
keeps contradicting expectations sh The heliosphere itself has an asymmetric
1:44:20
shape that reveals interstellar magnetic field influence. It's not a
1:44:25
perfect sphere expanding equally in all directions. Instead, the interstellar
1:44:32
magnetic field drapes around the heliosphere, creating higher magnetic pressure
1:44:38
on one side. That pressure pushes the boundary inward. The
1:44:43
southern part of the heliosphere gets compressed more than other regions.
1:44:49
The termination shock isn't centered on the Sun. It's offset
1:44:54
about thirty two astronomical units tailward, twenty seven units north,
1:45:00
twelve units to the port side. The Interstellar Boundary Explorer
1:45:05
confirmed these offsets independently. The closest region of the termination
1:45:10
shock sits roughly twenty degrees south of the interstellar inflow
1:45:15
direction minimum distance around seventy four astronomical units. That asymmetry
1:45:22
reveals how external forces shape the Sun's protective bubble. The
1:45:28
heliosphere responds to pressure from outside, gets pushed and deformed,
1:45:34
becomes lobsided rather than symmetric. This shape resembles a comet
1:45:40
more than a sphere, roughly spherical on one side, extending
1:45:45
about one hundred astronomical units, but on the opposite side
1:45:50
a tail stretches for thousands of astronomical units. The heliotail
1:45:56
a vast stream of solar material trailing behind, as are
1:46:00
the solar system moves through the galaxy. Voyager is heading
1:46:04
toward the nose of this comet shape, the front where
1:46:09
the heliosphere pushes against oncoming interstellar material. The tail extends
1:46:16
in the opposite direction, far beyond where any spacecraft will
1:46:20
travel for centuries. The heliosphere also changes over time. It's
1:46:26
not static. The Sun's eleven year activity cycle affects everything.
1:46:32
During solar maximum, increased solar wind output makes the heliosphere larger.
1:46:38
During solar minimum, reduced output lets it contract like a lung,
1:46:44
expanding and contracting with breath. The boundary moves. The heliopause
1:46:51
isn't fixed at one distance. Future spacecraft crossing it might
1:46:57
find it at different locations depending on where the Sun
1:47:02
is in its cycle. This dynamic nature means Voyager's measurements
1:47:07
capture the heliosphere at specific moments in its breathing cycle.
1:47:13
Voyager one cross during different solar conditions than the Voyager two.
1:47:19
That partially explains why their crossings showed different characteristics. They
1:47:25
sample the boundary at different times, different solar wind conditions,
1:47:31
different states of the heliosphere's expansion and contraction. Inside the heliosphere,
1:47:38
plasma is hot and sparse. Solar wind creates this environment
1:47:43
millions of degrees kelvin but extremely low density. Outside, interstellar
1:47:49
plasma is colder but denser. That fundamental difference marks the
1:47:54
transition from solar dominated to interstellar dominated environment. Different temperature,
1:48:02
different density, different composition. The properties flip at the boundary.
1:48:09
Hot sparse plasma inside gets continuously replenished by solar wind
1:48:14
streaming outward. The Sun constantly pumps new material into the heliosphere,
1:48:21
maintains the pressure keeps the bubble inflated. Without that continuous flow,
1:48:28
the heliosphere would collapse interstellar pressure would overwhelm it, but
1:48:37
the Sun's output continues the wind flows, the bubble persists.
1:48:44
The colder, denser interstellar plasma is part of the local
1:48:48
interstellar cloud. Our solar system currently travels through That cloud
1:48:54
has its own properties, its own density and temperature, its
1:48:59
own magnetic field structure. The heliosphere moves through this cloud
1:49:05
like a submarine through ocean water. The cloud's properties determine
1:49:11
how strongly it pushes back against the heliosphere, how much
1:49:16
it compresses our protective bubble. Understanding these plasma properties helps
1:49:22
scientists model stellar wind interactions everywhere, not just for our Sun.
1:49:29
Every star with a wind creates its own heliosphere like structure.
1:49:35
Different stars, different wind strengths, different surrounding environments, but the
1:49:41
basic physics remains similar. What Voyager learns about our heliosphere
1:49:47
applies to understanding how other stars interact with their galactic neighborhoods.
1:49:54
One curious finding the very local interstellar medium appears remark quiet.
1:50:01
Voyager one measured very small magnetic fluctuation intensity beyond the heliopause.
1:50:09
Scientists expected more turbulence, more variation, more chaos in the
1:50:14
magnetic fields. Instead, the interstellar medium right outside our heliosphere
1:50:20
shows surprising calmness. The fields are relatively steady, the fluctuations
1:50:27
are minimal. Why so quiet that remains unclear. Maybe we're
1:50:33
in an unusually calm region of the local interstellar cloud.
1:50:40
Maybe the heliosphere itself affects nearby interstellar space, creating a
1:50:45
carmozoone immediately outside the boundary. Or maybe current instruments aren't
1:50:53
sensitive enough to detect smaller scale turbulence that exists. But
1:50:59
the measures show less variation than expected. Another's surprise to
1:51:06
add to the list. In twenty twenty, both spacecraft recorded
1:51:13
something new. Voyager one's magnetometer registered an abrupt jump in
1:51:19
magnetic field intensity, its plasma detector measured rising plasma density.
1:51:25
At first, researchers attributed these changes to solar effects, surges
1:51:32
of solar plasma smashing against the heliosphere boundary, creating swells
1:51:37
that reverberate through interstellar space, compression waves from the Sun
1:51:43
reaching beyond the heliopause, temporary disturbances from our star's activity.
1:51:49
But the anomalies didn't abate. They continued persisted far longer
1:51:55
than expected. That raised questions if these changes came from
1:52:00
the Sun, they should be temporary, transient effects that pass
1:52:05
as the solar disturbance moves by. Instead, the elevated fields
1:52:10
and density remained months past. The reading stayed high. Some mission.
1:52:18
Scientists began questioning whether the Sun caused these changes at all.
1:52:23
Maybe Voyager encountered something else entirely, a new type of
1:52:29
interstellar structure, a region of naturally higher density in the
1:52:35
local interstellar medium, or perhaps some other phenomenon scientists haven't
1:52:41
yet identified. The mystery remains unsolved. Data continues arriving, scientists
1:52:49
keep analyzing, but no definitive explanation has emerged. This demonstrates
1:52:55
that even after crossing into interstellar space, Voyage keeps encountering
1:53:01
unexpected phenomena. The journey doesn't end at the heliopause. New
1:53:07
discoveries wait farther out. The interstellar medium has its own complexity,
1:53:14
its own structures, its own mysteries to reveal. October twenty
1:53:19
twenty brought another significant finding. Both spacecraft detected a substantial,
1:53:26
unexpected increase in density beyond the Solar System. The measurements
1:53:32
suggested this density gradient is a large scale feature of
1:53:37
the very local interstellar medium in the direction of the
1:53:42
heliospheric nose, not a temporary anomaly, not a local fluctuation,
1:53:50
but a genuine trend increasing density as Voyager travels farther
1:53:57
into interstellar space. This increasing density has implications. It suggests
1:54:04
the local interstellar medium isn't uniform. Density varies. Maybe the
1:54:10
medium is being compressed ahead of the heliosphere, Maybe our
1:54:15
solar system approaches a denser region of the interstellar cloud,
1:54:20
or maybe the structure of the cloud itself naturally has
1:54:24
density variations that Voyager is now sampling. Whatever the cause,
1:54:30
the discovery challenges assumptions about a uniform interstellar medium. Space
1:54:36
between stars has structure, has variation changes from place to place.
1:54:42
These measurements help scientists understand the local interstellar cloud through
1:54:48
which our solar system moves. That cloud has boundaries, has
1:54:54
internal structure, has regions of different density and temperature. Voyager
1:55:01
is mapping it one measurement at a time. Each data
1:55:06
point adds detail to our understanding of the neighborhood through
1:55:10
which the Sun travels. The spacecraft also detected what scientists
1:55:15
call interstellar flux tubes, structures where particles from outside somehow
1:55:22
intrude into the heliosphere before the heliopause. Voyager detected interstellar
1:55:29
particles on two separate occasions while still technically inside the boundary.
1:55:36
How did those particles get there? The flux tubes temporary
1:55:40
channels or filaments that allow interstellar material to penetrate the heliopause,
1:55:47
like leaks in the hull of a ship. One of
1:55:50
Voyager's instruments showed particles from inside the heliosphere slipping through
1:55:56
the boundary into interstellar space. The boundary leaks both ways,
1:56:02
not perfectly sealed, not a solid wall, more porous than
1:56:07
simple models suggested, and the permeability varies by location. Voyager
1:56:13
one exited near the front of the heliosphere, the nose
1:56:17
pushing into oncoming interstellar flow. That region appears more tightly sealed.
1:56:25
Voyager two crossed closer to the flank. That region seems
1:56:31
more porous, easier for particles to cross, more leakage in
1:56:37
both directions. This asymmetric permeability reveals the boundary's complexity. It's
1:56:44
not uniform. Properties change depending on location. Some regions are tighter,
1:56:51
others more porous. The structure depends on local magnetic field geometry,
1:56:57
on the angle between solar and in interstellar fields, on
1:57:02
pressure variations around the boundary. All these factors create a
1:57:07
complicated three dimensional structure that varies from place to place.
1:57:13
The discovery challenges the notion of the heliopause as an
1:57:17
impermeable boundary. It's more like a fuzzy transition zone with
1:57:22
varying properties. Particles can cross under certain conditions in certain locations.
1:57:30
The boundary exists, but it's not absolute, not perfectly defined,
1:57:36
more nuanced than early models suggested. Both Voyager crossings showed
1:57:41
increased plasma density before and after the boundary compression on
1:57:47
both sides higher than expected density. This suggests interstellar pressure
1:57:54
shapes the heliospheres outer layers more actively than models predicted.
1:58:00
The interstellar medium pushes back harder, compresses the boundary region,
1:58:06
creates density enhancements both inside and outside the heliopause. That
1:58:12
compression affects how the boundary behaves, affects its permeability, affects
1:58:18
particle acceleration near the boundary, affects magnetic field behavior. The
1:58:25
pressure from outside influences everything about how the heliosphere's edge
1:58:30
forms and evolves. Scientists are incorporating these observations into updated models,
1:58:38
trying to capture the complexity Voyager revealed.
1:58:42
Speaker 2: Every discovery raises.
1:58:44
Speaker 1: New questions, every answer reveals deeper mysteries. The spacecraft keep traveling,
1:58:51
keep measuring, keep sending data back across billions of kilometers,
1:58:56
and scientists keep learning, keep reval advising theories, keep uncovering
1:59:03
how our solar system fits into its galactic environment. The
1:59:07
edge of the Solar system isn't simple, isn't clean, isn't predictable.
1:59:13
It's a dynamic, complex, surprising place where solar influence fades
1:59:19
and galactic environment begins, Where two different plasma environments meet
1:59:25
and interact, Where boundaries leak and compress and shift over time,
1:59:32
Where spacecraft designed in the nineteen seventies continue revealing secrets
1:59:39
no one anticipated when the mission launched. Yet there's something
1:59:43
stranger happening further out, something that puzzles mission scientists even now.
1:59:50
In twenty twenty, Voyager one's magnetometer registered an abrupt jump
1:59:57
in magnetic field intensity, not during a solar outburst, not
2:00:02
during any obvious event. The intensity just increased and stayed elevated.
2:00:08
Plasma density rose simultaneously, two separate instruments showing correlated changes.
2:00:15
Scientists initially thought solar eruptions caused it. The Sun periodically
2:00:20
ejects massive plasma clouds. Those clouds slam into the heliopause,
2:00:28
create pressure waves that propagate outward into interstellar space, compress
2:00:35
the interstellar plasma intensify its magnetic field. That explanation worked
2:00:42
for the first few events, but the anomalies that began
2:00:45
in twenty twenty didn't abate. They persisted month after month,
2:00:52
year after year. Mission scientists started questioning the solar origin hypothesis.
2:01:00
If these changes came from the Sun, they should be transient, temporary,
2:01:05
fading as the pressure wave passes, But Voyager keeps measuring
2:01:10
elevated field strength, higher density, something sustained.
2:01:16
Speaker 2: Does Voyager one travel through.
2:01:17
Speaker 1: A new type of interstellar structure, a region where the
2:01:23
local interstellar medium naturally has higher density or stronger magnetic fields,
2:01:32
or does the Sun's influence extend further than models predict,
2:01:36
creating long lasting effects beyond the heliopause. No definitive answer yet,
2:01:43
just ongoing measurements, continued mystery, another example of how interstellar
2:01:50
space refuses to match predictions. Meanwhile, the spacecraft themselves approach
2:01:56
their inevitable silence, not from dramatic failure from simple power depletion.
2:02:03
Voyager one and two carry plutonium two hundred thirty eight
2:02:07
radio isotope thermoelectric generators. The plutonium decays generates heat, thermocouples
2:02:16
convert that heat to electricity. Elegant system, no moving parts,
2:02:21
no sunlight required, perfect for deep space missions lasting decades,
2:02:26
but plutonium decays constantly, heat output drops, available power decreases
2:02:34
year by year. Engineers have managed the decline carefully, turning
2:02:39
off heaters, shutting down non essential systems, prioritizing the science
2:02:45
instruments that provide unique data from interstellar space. As of
2:02:51
early twenty twenty six, Voyager one sits at one hundred
2:02:56
seventy two astronomical units from Earth, Voyager two at one
2:03:01
hundred forty three astronomical units, both still functioning, still transmitting,
2:03:08
still measuring the interstellar environment. Each generates approximately two hundred
2:03:14
and twenty wards, down from four hundred and seventy wards
2:03:18
at launch. Not much power a couple of old fashioned
2:03:22
incandescent bulbs that dwindling supply determines mission longevity, not instrument failure,
2:03:30
not communication loss, just insufficient power to run the instruments
2:03:36
and transmitted data back. Mission managers estimate the spacecraft can
2:03:41
operate into the early twenty thirties, maybe a few years
2:03:46
longer with careful power management. Then the final instruments will
2:03:50
shut down. Signals will cease. The spacecraft will continue coasting outward,
2:03:58
silent dark, carrying their golden records, messages from Earth encased
2:04:03
in gold plated copper, images, sounds, music, greetings in fifty
2:04:09
five languages. Those records will outlast Earth itself, probably outlast
2:04:15
the Sun. Voyager one and two will orbit the Galactic
2:04:20
center for billions of years, occasionally passing through interstellar clouds,
2:04:28
sometimes encountering other stars, heliopores, regions, always moving, never returning.
2:04:37
But before silence falls, the data keeps flowing. Every measurement
2:04:42
adds detail, Every observation refines models, Every anomaly reveals how
2:04:48
much remains unknown. Consider what Voyager has accomplished. Two spacecraft
2:04:55
launched in nineteen seventy seven, built with nineteen seventies technology,
2:05:00
before personal computers, before the Internet, before cell phones, before
2:05:06
digital cameras. Those spacecraft explored Jupiter, discovered active volcanoes on Io,
2:05:14
revealed the intricate structure of Saturn's rings, found new moons,
2:05:19
measured planetary magnetic fields, revolutionized understanding of the outer Solar System.
2:05:25
Then kept going into regions never before explored past Neptune,
2:05:31
pass Pluto into the Helio sheath through the heliopores into
2:05:38
interstellar space itself. They've traveled longer than any human mission, operated,
2:05:44
longer than any spacecraft, returned data from further away than
2:05:49
any probe before them, and they've revealed that the edge
2:05:54
of the Solar System isn't what anyone expected. Not clean,
2:05:59
not simple, not predictable, A complex, dynamic, surprising boundary where
2:06:05
solar dominance fades and galactic environment takes over.
2:06:09
Speaker 2: The Heliosphere itself.
2:06:11
Speaker 1: Appears more complicated than models suggested. Not spherical, not static,
2:06:17
asymmetric variable responding to solar activity, shape by interstellar pressure,
2:06:24
compressed in some directions, extended in others. The heliopause leaks
2:06:29
particles cross in both directions. Magnetic fields align unexpectedly, temperature
2:06:36
varies wildly, density changes unpredictably. Everything about the boundary challenges
2:06:43
simple descriptions. Scientists once thought they understood heliospheres. The Sun
2:06:50
creates one. Other stars probably create similar structures. Simple concept,
2:06:57
straightforward physics. Voyager showed otherwise, the details matter, The complexity matters.
2:07:05
Every heliosphere likely differs based on its star's output and
2:07:10
the interstellar environment it encounters. That knowledge extends beyond our
2:07:15
Solar system helps Astronomers understand exoplanet environments, stellar winds around
2:07:23
other stars, how cosmic rays affect planetary atmospheres, the habitability
2:07:31
of worlds orbiting different types of stars. The heliosphere shields
2:07:37
Earth from most galactic cosmic rays. Voyager one measured that
2:07:42
protection over seventy percent reduction. Without that shield, Earth's atmosphere
2:07:49
would receive far more radiation. Life's evolution might have taken
2:07:54
different paths, or struggled to develop at all. Other stars
2:08:00
have different winds, different magnetic fields create different heliospheres. Some
2:08:07
might offer less protection, others more. The details shape whether
2:08:12
planets can maintain atmospheres, whether life can thrive. Voyagers measurements
2:08:19
provide the ground truth, the actual data against which models
2:08:24
are tested. Future missions to other stars will need to
2:08:29
account for these complexities, and the spacecraft still have more
2:08:34
to teach as they continue outward. They'll measure how the
2:08:39
very local interstellar medium varies, map density gradients, track magnetic
2:08:46
field changes, detect structures in the local interstellar cloud that cloud.
2:08:52
The local interstellar cloud extends for several light years. Our
2:08:58
solar system entered it thousands of years ago, will remain
2:09:03
inside for thousands more voyager samples its properties, measures its structure,
2:09:13
provides data no other mission can. Eventually, the spacecraft will
2:09:19
pass through the cloud's far boundary enter different interstellar regions,
2:09:26
but their power will likely fail before reaching that transition.
2:09:30
The data stream will end while still inside the local cloud.
2:09:35
What comes after silence just trajectory. Voyager one heads toward
2:09:41
the constellation Ophiocus, will pass within one point six light
2:09:46
years of the star Gleiser four four or five in
2:09:50
about forty thousand years, not close enough to be captured,
2:09:55
just passing through that star's neighborhood. Voyager two, heads towards Sirius,
2:10:02
will come within four point three light years in about
2:10:05
two hundred ninety six thousand years, Again not close enough
2:10:11
for gravitational capture. Just another waypoint in eternal wandering. Both
2:10:17
spacecraft will orbit the galaxy, rising and falling through the
2:10:22
galactic disk, passing through spiral arms, occasionally encountering molecular clouds,
2:10:30
always moving at about seventeen kilometers per second relative to
2:10:34
the Sun, that velocity insufficient for escaping the galaxy, too
2:10:40
fast for stellar capture. They'll witness events no human will
2:10:45
see stellar evolution, supernova explosions from relatively close range, the
2:10:52
slow transformation of galactic structure, the eventual collision between Milky
2:10:57
Way and Andromeda galaxies in four billion years, silent witnesses
2:11:03
to cosmic history, carrying humanity's message, a gesture of communication
2:11:09
from a species that briefly emerged on one world, looked outward,
2:11:14
built machines to explore and send them into the infinite.
2:11:19
The Golden Records preserve that moment nineteen seventy seven, when
2:11:25
humans could launch such missions, when the planets aligned favorably,
2:11:30
when technology and ambition converged, when two spacecraft began journeys
2:11:36
that continue five decades later. Those records contain images of Earth,
2:11:42
mathematical definitions, the structure of DNA, photographs showing human diversity,
2:11:49
sounds of nature, music spanning cultures and centuries, Greetings speaking
2:11:55
humanity's linguistic diversity. Any civilization finding these spacecraft millions or
2:12:03
billions of years hence, will discover artifacts from a vanished world.
2:12:10
They'll decode the instructions play the records encounter humanity through
2:12:16
carefully curated messages. Will they understand? Possibly? The records include
2:12:23
mathematical and scientific information, universal constant physical principles, Any technological
2:12:31
civilization should recognize. Will they care unknown. Perhaps they'll find
2:12:37
these ancient probes archaeologically interesting, perhaps merely puzzling. Perhaps they'll
2:12:44
never be found at all. Drifting eternally through interstellar space,
2:12:49
passing between stars without notice, But the gesture matters. The
2:12:54
attempt to communicate across cosmic distances and timescales represents something
2:13:01
fundamental about human nature. The drive to explore, to reach
2:13:06
beyond known boundaries, to leave traces proving we existed. Voyager
2:13:12
embodies that drive, two spacecraft carrying our message, our science,
2:13:17
our curiosity, our hope that someone somewhere sometime might find them,
2:13:24
and no. Humanity briefly flourished, and until that distant possibility,
2:13:30
the mission continues. Data flows, scientists analyze, Knowledge grows, the
2:13:38
edge of the Solar system reveals itself, measurement by measurement,
2:13:43
the boundary between solar and galactic environments becomes clearer. The
2:13:48
complexity deepens. Every discovery raises questions, Every answer reveals deeper mysteries.
2:13:57
The universe refuses to be simple, refuses to match predictions,
2:14:04
continues surprising us. That's the real legacy, not the distance traveled,
2:14:10
not the longevity, the revelation that even familiar territory, the
2:14:16
space around our own Sun, contains profound mysteries, that boundaries
2:14:21
are complex, that nature resists simple categorization. The Solar system
2:14:27
has no clean edge, no definite ending, just gradual transition
2:14:33
from solar dominance to galactic environment, multiple boundaries, overlapping regions,
2:14:40
asymmetric structure, temporal variation, spatial complexity. Voyager showed us that
2:14:47
truth continues, showing us We'll keep revealing details until power
2:14:53
finally fails and silence falls. And even then, the spacecraft
2:14:59
keep going, moving outward, carrying their messages, traversing the galaxy
2:15:05
for epochs beyond human comprehension, physical embodiments of humanity's brief
2:15:11
moment of consciousness and curiosity, our emissaries to Eternity, our
2:15:18
footprints in the cosmic sand. The spacecraft keep transmitting, keep measuring,
2:15:25
keep sending data back across distances that take over twenty
2:15:29
three hours for light to cross. That delay matters. When
2:15:34
scientists send a command to Voyager one, it takes twenty
2:15:38
three hours to arrive. The spacecraft executes, the command, sends
2:15:44
confirmation back another twenty three hours, nearly two full days
2:15:49
for a single exchange, a conversation stretched across billions of
2:15:53
kilometers at the speed of light itself, Yet that conversation continues.
2:16:00
Engineers monitor power levels, adjust instrument operations, prioritize data collection,
2:16:07
maximize what little time remains, because the end approaches, not suddenly,
2:16:14
not catastrophically, just the steady, inevitable decline of plutonium two
2:16:20
hundred and thirty eight decaying in the radio isotope generators,
2:16:25
heat output dropping, available electricity decreasing by the early twenty thirties,
2:16:32
maybe a few years beyond. With careful management, insufficient power
2:16:36
will remain. The last instrument will shut down, the final
2:16:41
transmission will cease, then silence, not failure, not loss, just completion.
2:16:49
The mission will have extracted every possible measurement from humanity's
2:16:55
first journey into interstellar space. Conser what those measurements revealed,
2:17:02
a boundary far more complex than anticipated. A helio pause
2:17:07
that leaks, that shifts, that varies by location and time,
2:17:13
temperature extremes, creating a wall of fire where charge particles
2:17:18
compress and heat to tens of thousands of degrees while
2:17:22
adjacent regions stay cool. Magnetic fields that align impossibly cosmic
2:17:30
rays that intensify beyond where models predicted, plasma densities that
2:17:35
jump eightyfold at the boundary, solar wind that sometimes flows
2:17:40
backward a stagnation region.
2:17:43
Speaker 2: Nobody expected.
2:17:45
Speaker 1: Interstellar structures detected through persistent density changes and magnetic field anomalies.
2:17:53
Every discovery challenged assumptions. Every measurement revealed complexity the air
2:18:00
each of the Solar System refused to match the clean,
2:18:03
simple picture scientists had constructed. That's the deeper lesson reality
2:18:09
exceeds models. Nature resists simplification. The universe contains layers of
2:18:16
complexity that reveal themselves only through direct observation. No amount
2:18:23
of theoretical work could have predicted what Voyager found. The
2:18:28
calculations were elegant, the simulations sophisticated, the predictions logical, and
2:18:37
substantially wrong about crucial details. Only by going there, actually
2:18:43
traveling to the boundary and measuring it directly, could scientists
2:18:48
discover what truly exists at the Solar System's edge. This
2:18:53
principle extends beyond heliospheres. It applies everywhere, to planetary atmospheres,
2:19:01
to stellar evolution, to galactic dynamics, to cosmic structure formation theory, guides.
2:19:09
Observation corrects direct measurement reveals truth that mathematics alone cannot capture.
2:19:16
Voyager one and two demonstrated that principle at the grandest
2:19:21
scale yet attempted. They ventured into the unknown and found
2:19:26
it stranger than imagined. The spacecraft also revealed something about
2:19:32
human capability. In nineteen seventy seven, engineers build two probes
2:19:39
using technology that seems primitive by modern standards. Computers with
2:19:44
less processing power than a contemporary calculator, instruments that could
2:19:49
fit in a suitcase, power systems generating barely more electricity
2:19:55
than a couple of light bulbs. Those machines operated fl
2:20:00
lawlessly for five decades, survived radiation, extreme cold, micrometeorite impacts,
2:20:07
the accumulated damage of fifty years in space. They kept functioning,
2:20:12
kept transmitting, kept delivering science. Modern spacecraft often fail within years,
2:20:19
sometimes months. The Voyagers persist not through luck, through brilliant design,
2:20:26
through engineering that prioritized reliability over capability, through systems built
2:20:33
to last when lasting meant everything. The golden records they
2:20:38
carry represent a different kind of achievement, not technological, cultural philosophical.
2:20:48
The decision to include messages for potential alien civilizations showed
2:20:53
humanity at its most optimistic, most hopeful, most willing to
2:20:59
believe in possibility beyond immediate evidence. Those records preserve a
2:21:05
moment nineteen seventy seven when humans looked outward with wonder
2:21:11
rather than fear, when space explorations seemed limited only by imagination,
2:21:17
when the future felt infinite. The messages encoded on gold
2:21:21
plated copper include mathematical principles, images of Earth, sounds of nature,
2:21:29
music spanning cultures, greetings in fifty five languages. Carl Sagan
2:21:36
and his team carefully curated content representing humanity's diversity and achievement.
2:21:45
Any civilization finding these artifacts millions of years hence will
2:21:51
encounter humanity frozen in that moment of optimism. They won't
2:21:57
know what came after, won't know where the humans survived,
2:22:02
whether we spread through the cosmos or destroyed ourselves, whether
2:22:07
we ever developed interstellar travel or remained confined to one
2:22:12
star system.
2:22:14
Speaker 2: They'll only know we existed.
2:22:17
Speaker 1: We built these machines, We sent them into the void
2:22:21
carrying messages. We hoped someone might find them and understand
2:22:27
that hope matters more than the probability of discovery.
2:22:32
Speaker 2: The gesture itself, the act.
2:22:34
Speaker 1: Of reaching across cosmic distances and timescales, defines something essential
2:22:40
about human consciousness. We seek connection, We want to be known.
2:22:45
We refuse to accept isolation, even when separated by light
2:22:49
years and eons. Voyager embodies that refusal. Two spacecraft carrying
2:22:57
Humanity's message into a turn wandering, not because the message
2:23:03
will likely be received, because sending it affirms our existence,
2:23:09
our curiosity, our hope. Meanwhile, the science continues. Every remaining
2:23:16
day of operation adds value. The spacecraft measure how the
2:23:21
very local interstellar medium varies, how density changes with distance
2:23:27
from the heliopores, how magnetic fields evolve in interstellar space,
2:23:33
how the local interstellar cloud structure affects its properties. These
2:23:39
measurements can't be obtained any other way. No telescope can
2:23:44
resolve such fine detail at interstellar distances, No model can
2:23:49
predict variations with our ground truth for calibration. Only by
2:23:54
traveling through the region and measuring it directly can scienceists
2:24:00
map its properties. Voyager provides that irreplaceable data. The spacecraft's
2:24:07
sample the interstellar environment, record its characteristics, transmit findings back
2:24:14
across billions of kilometers Each data point adds detail to
2:24:19
humanity's understanding of the space between stars. That space isn't empty,
2:24:26
isn't uniform, isn't boring. It contains structure variation, complexity matching
2:24:33
anything found within solar systems. The interstellar medium has its
2:24:38
own dynamics, its own weather, its own mysteries. Scientists once
2:24:43
viewed it as mere background, empty space between interesting objects.
2:24:50
Voyager revealed otherwise, interstellar space has properties worth studying, structures
2:24:58
worth mapping, worth understanding. The very local interstellar medium through
2:25:04
which Voyager travels right now, the region immediately beyond the
2:25:10
heliopores differs from the wider interstellar medium. It's been shaped
2:25:16
by interaction with the heliosphere, compressed by pressure from the
2:25:22
solar wind, modified by magnetic fields from the Sun. This
2:25:27
boundary region extends for multiple astronomical units beyond the heliopause.
2:25:33
Voyager is mapping it, measuring how properties transition from nearly
2:25:38
solar to fully interstellar, how the Sun's influence fades with distance,
2:25:47
where galactic environment finally dominates completely. Future missions might follow
2:25:54
Voyager's path. New spacecraft with more advanced instruments, better power systems,
2:26:02
upgraded communications. They'll build on Voyagers discoveries explore regions Voyager
2:26:11
couldn't reach. Answer questions Voyager raised, but they'll do so
2:26:17
decades from now, maybe longer. Currently, no funded mission targets
2:26:22
interstellar space. No spacecraft capable of reaching the heliopause within
2:26:28
human lifetimes exists beyond Voyager itself. The New Horizon's Probe,
2:26:34
which explored Pluto, continues outward. It might eventually reach the heliopause,
2:26:42
but not for decades, and it carries fewer functioning instruments
2:26:46
than Voyager, less power, shorter operational life expectancy. So Voyager
2:26:53
remains humanity's primary source of direct interstellar measurements, the only
2:26:59
functioning space craft beyond the Solar System's edge, the sole
2:27:04
providers of ground truth about what exists out there. When
2:27:09
the spacecraft finally falls silent, their data stream ends, scientists
2:27:15
will retain everything transmitted, will analyze it for years, extract
2:27:21
every possible insight, but no new measurements will arrive. The
2:27:27
exploration of interstellar space will pause until someone launches the
2:27:33
next mission, until technology and funding a line, until humanity
2:27:39
again commits resources to exploring beyond the Solar System's boundary.
2:27:44
That commitment seems uncertain space exploration budgets remain modest. Priorities
2:27:51
shift decades, separate major missions. Interstellar probes require patients commitmentness
2:28:00
to support projects that won't return results within single careers
2:28:05
or lifetimes. Voyager demonstrated what such commitment achieves, what patience enables,
2:28:13
what results from building machines designed to last and supporting
2:28:18
them across decades. The spacecraft launched before personal computers existed,
2:28:24
before the Internet, before cell phones, before digital photography, using
2:28:30
technology that seems ancient now, Yet they still function, still explore,
2:28:36
still return signs impossible to obtain any other way. That
2:28:41
achievement stands regardless of what follows. Voyager one and two
2:28:48
accomplished their mission. Explored the outer planets, reached interstellar space,
2:28:54
measured the boundary, revealed its complexity, transmitted data that transformed
2:29:00
understanding Everything beyond this point is bonus extended mission, unexpected longevity,
2:29:09
additional science from regions. No mission planner in nineteen seventy
2:29:14
seven imagine the spacecraft would reach. The plutonium keeps decaying,
2:29:20
the power keeps dropping, the end keeps approaching, But until
2:29:25
that moment arrives, Voyager continues its primary function, measuring recording,
2:29:32
transmitting teaching humanity about the cosmos we inhabit. The wall
2:29:37
of fire at the Solar system's edge turned out to
2:29:41
be real, not metaphorical. Actual superheated plasma reaching tens of
2:29:47
thousands of degrees, trapped particles compressed at the boundary, creating
2:29:54
temperature extremes that defy simple explanation. Space Craft survived only
2:30:02
because the density is too low to transfer heat effectively.
2:30:08
The fire exists but cannot burn, cannot damage, can only
2:30:15
be measured and marveled at. That paradox captures something about
2:30:20
the boundary itself. It exists definitively measurably, yet its more
2:30:27
complex than simple existence suggests more nuanced than any single
2:30:32
description captures. The heliopause is a boundary, but also a
2:30:37
transition zone, a region of mixing and interaction, a dynamic
2:30:42
interface responding to pressure from both sides. It shifts position,
2:30:48
changes character, varies by location, leaks particles in both directions.
2:30:54
Defining where the Solar system ends becomes surprisingly difficult when
2:30:59
examined closely. The heliopause marks one boundary, but solar wind
2:31:05
continues beyond it. Briefly, cosmic rays penetrate inward from it,
2:31:11
magnetic fields connect across it. The transition isn't instantaneous or complete.
2:31:17
Perhaps that's the fundamental insight. Nature doesn't do clean boundaries,
2:31:24
doesn't create sharp divisions, produces gradients instead, transition zones, regions
2:31:31
where properties shift gradually or chaotically, but rarely instantaneously. The
2:31:38
Solar system doesn't end at a specific distance. It fades,
2:31:42
its influence diminishes, galactic environment gradually dominates. Multiple boundaries exist, termination, shock, heliopores,
2:31:53
hydrogen wall, each marking different aspects of the transition. Voyager
2:31:58
mapped those boundaries, measured them, revealed their complexity, showed that
2:32:04
even the space around our own star contains profound mysteries.
2:32:09
And the spacecraft keep going outward, always outward, measuring what
2:32:15
they can, transmitting what they measure, until power fails and
2:32:23
silence falls. Then they'll continue without us, without communication, without
2:32:29
awareness of their own journey, just inert machines coasting through
2:32:35
the galaxy, carrying messages from a world they'll never revisit,
2:32:40
traveling distances they'll never comprehend. In forty thousand years, Voyager
2:32:46
one passes near Gleisa four four or five. In two
2:32:50
hundred and ninety six, thousand years, Voyager two approaches Sirius.
2:32:56
Distant future encounters with other stars, other Solar systems, other
2:33:01
potential heliopause boundaries, But those crossings will happen in silence,
2:33:07
no instruments to measure them, no transmitters to report findings,
2:33:12
just two ancient spacecraft drifting past, carrying gold records from
2:33:17
a civilization long gone, unless humanity survives that long, unless
2:33:24
we spread through the galaxy ourselves, unless our descendants encounter
2:33:30
Voyager wandering the cosmic depths and retrieve it, bring it home,
2:33:35
place it in a museum celebrating the first human made
2:33:39
objects to leave the Solar System.
2:33:43
Speaker 2: That future seems.
2:33:44
Speaker 1: Distant, speculative, uncertain, But so did interstellar travel. In nineteen
2:33:51
seventy seven, When Voyager launched, the spacecraft proved it possible,
2:33:56
not practical, perhaps, not easy, certainly, but possible. Two machines
2:34:02
built with nineteen seventies technology reached interstellar space and survived there,
2:34:09
operated there, return science from there. If machines build fifty
2:34:15
years ago, can achieve that, what might machines build fifty
2:34:20
years hence accomplish? What might humans themselves accomplish given sufficient
2:34:26
time and determination. Voyager suggests the answer, we can reach
2:34:34
beyond our Solar system, can explore interstellar space directly, can
2:34:40
measure what exists out there, and transmit that knowledge home.
2:34:45
The question isn't whether we can, it's whether we will,
2:34:50
whether we'll commit resources to such endeavors, whether we'll maintain
2:34:55
patients across decades required for results, whether we'll value knowledge
2:35:00
for its own sake enough to pursue it into the
2:35:04
cosmic dark. Voyager demonstrates, we once did one's prioritized exploration,
2:35:12
one's built machines to last, one sent them into the unknown.
2:35:17
Speaker 2: Because the unknown beckoned.
2:35:19
Speaker 1: The spacecraft continue that journey now, measuring, recording, transmitting, teaching,
2:35:27
revealing until the day they can't, until power fails and
2:35:32
silence claims them. But the data survives, the knowledge endures,
2:35:37
the discoveries remain. Humanity learned what exists at the solar
2:35:42
system's edge because two spacecraft traveled there and measured it directly.
2:35:48
That achievement stands permanent whatever follows, whether new missions or
2:35:55
decades of silence. Voyager proved it possible, showed the way,
2:36:00
revealed what awaits beyond the boundary.
2:36:04
Speaker 2: The wall of fire is real.
2:36:06
Speaker 1: The boundary is complex interstellar space beckons, and we've touched
2:36:11
it briefly, tentatively, but genuinely. Two spacecraft from Earth crossed
2:36:18
into the space between stars and survived to report what
2:36:22
they found. That's the story, that's the achievement. That's what
2:36:28
Voyager revealed. At the edge of our solar system, where
2:36:32
solar influence fades and the galaxy begins.