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Narrator: The two Voyager spacecraft have been traveling away

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from Earth for more than 33 years and they are finally in the outer edge of the solar

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system. This boundary is marked by the outer reaches of the sun's

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magnetic field and solar wind, which form an enormous expanse called the heliosphere.

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As the solar wind travels out from the sun, it pushes against the galactic

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medium and abruptly slows down.  This is called the termination shock.

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Outside this is the heliosheath, where the solar wind slows to a stop

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and the magnetic field is bent back by the ionized interstellar wind.

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The sun's magnetic field spins opposite directions

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on the north and south poles, creating a sheet where the two spins meet.

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This sheet gently ripples as it travels outward and the ripples get bigger

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as they go. When this sheet reaches the termination

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shock, it starts to compress, like water waves hitting a wall.

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The Voyager spacecraft have now found that after the termination shock, these stacked-up

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ripples of magnetic field form bubbles, shown here as a computer simulation.

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This discovery has prompted a complete

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revision of what the heliosheath region looks like. The smooth streamlined look is

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gone, replaced with a bubbly, frothy outer layer. This new layer

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also changes our understanding of how extremely fast-moving particles called cosmic

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rays enter our solar system.  When they arrive at the bubble region,

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they slowly move from bubble to bubble until they can reach smooth magnetic field lines and

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follow them toward the sun. The nature of the bubble region explains

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why Voyager II has been seeing variations in the number of energetic particles compared

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to Voyager I. Because of its path, Voyager II has been passing

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in and out of the bubble region. When it is in the region Voyager II sees

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many trapped cosmic rays and electrons. When it is out of the region

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the spacecraft sees fewer. Even as the Voyagers answer questions

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about our solar system, they raise others. For example, scientists

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aren't clear yet how the bubbly heliosheath is linked to the ribbon feature discovered by

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IBEX and Cassini. This ribbon shows the emission of energetic particles

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and seems to indicate some interaction with interstellar space.

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In the meantime, the Voyager spacecraft continue sending back data, and,

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after three decades, they still have a unique perspective to offer