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Voyager: The Great Adventure Continues

The twin Voyager spacecraft are now exploring the outer reaches of the solar system and beyond. A supersonic wind from the Sun creates a bubble in interstellar space called the heliosphere. Solar matter is dominant inside the heliosphere, while matter from other stars dominates outside.

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Planetary Tour video

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heliosphere, bow shock, solar winds, interstellar winds, solar apex, heliopause, termination shock

For the next two decades, the Voyager spacecraft will race to reach interstellar space while they still have enough electrical power to transmit data to Earth. In the next several years, Voyager 1 may pass the termination shock, the first feature on its journey to interstellar space.

Voyager 1

Voyager 1 is the most distant human-made object in the universe, twice as far from the Sun as Pluto. It was deflected northward above the plane of the planets' orbits when it swung by Saturn in 1980 and is now speeding outward from the Sun at nearly one million miles per day, a rate that would take it from Los Angeles to New York in less than four minutes. Long-lived nuclear batteries are expected to provide electrical power until at least 2020 when Voyager 1 will be more than 13 billion miles from Earth and may have reached interstellar space.

Voyager 1
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Fact sheet

Voyager 2

Voyager 2 has visited more planets than any other spacecraft, swinging by Jupiter, Saturn, Uranus and Neptune. Voyager 2 was deflected downward by Neptune and is heading southward below the plane of the planets. With a somewhat lower speed than Voyager 1, it is about eighty percent as far from the Sun.

Voyager 2
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Fact sheet


Our Sun is a star that holds about 99.9 percent of all the matter in the solar system. Its hot atmosphere expands supersonically outward, creating a flow of electrically charged ions called the solar wind that sweeps outward past all the planets at nearly one million miles per hour.

the Sun
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More Sun info

Please refer to the graphic below for the following definitions.


The supersonic solar wind of charged ions creates a bubble around the Sun called the heliosphere that extends far past the orbits of the planets. An external view of this bubble is represented by the yellow and green regions. A long wind-sock-like tail forms as the heliosphere moves with the Sun through interstellar space. The red arrows representing solar wind are seen being deflected at the front of the heliosphere, turning back and moving down the tail of the heliosphere.

Helioshpere and Termination Shock

Termination Shock

As the million-mile-per-hour solar wind approaches the boundary of the heliosphere, a termination shock, shown by the red circle, forms where the wind abruptly slows down to about 250,000 miles per hour. As the wind, indicated by the red arrows, continues beyond the termination shock, it turns and heads down the tail of the heliosphere.


As the solar wind expands outward from the sun, deep within the yellow sphere in this graphic, its pressure declines. The solar wind expands until its declining pressure balances the inward pressure of the surrounding interstellar matter. When this happens, the outward flow of the solar wind turns around the side of the heliospheric bubble. The heliopause is the resulting outer boundary of the heliosphere that separates the flows of the internal solar wind and the external interstellar wind.

Interstellar Wind

The moving white arrows illustrate a faint wind in nearby interstellar space that flows around the heliosphere, deforming it into a wind-sock-like shape.

Bow shock

As the heliosphere plows through the ionized interstellar gas, a bow shock forms, much as forms in front of a boulder in a stream.

Solar Apex Solar Apex

The solar apex is the direction toward which the Sun and the solar system are moving. The interstellar wind flows from a nearby direction. The heliosphere, with our solar system inside, is highlighted in this animation.