On August 25, 2012, NASA’s Voyager 1 spacecraft crossed the heliopause, the theoretical boundary of our solar system where the Sun’s solar wind is stopped by the interstellar medium, and became the first spacecraft in interstellar space.

Today’s (August 25) story of what happened this day in Science, Technology, Astronomy, and Space Exploration history.

Voyager 1: the first spacecraft in interstellar space

Voyager 1 is a space probe launched by NASA on September 5, 1977, 16 days after the August 20 launch of its twin, Voyager 2.

On December 19, 1977, Voyager 1 overtook Voyager 2. The two were sent on different trajectories, and Voyager 1 was put on a path to reach its planetary targets, Jupiter and Saturn, ahead of Voyager 2.

Heliosphere and Voyagers
This graphic shows the position of NASA’s Voyager 1 and Voyager 2 probes, outside of the heliosphere, a protective bubble created by the Sun that extends well past the orbit of Pluto. This illustration shows the position of NASA’s Voyager 1 (the first spacecraft in interstellar space) and Voyager 2 probes, outside of the heliosphere, a protective bubble created by the Sun that extends well past the orbit of Pluto. Voyager 1 crossed the heliopause, or the edge of the heliosphere, in August 2012. Heading in a different direction, Voyager 2 crossed another part of the heliopause in November 2018. One of the annotated images below shows plasma flow lines both inside and outside the heliopause. The direction of the solar plasma is different from the direction of the interstellar plasma. The Voyager spacecraft were built by JPL, which continues to operate both. JPL is a division of Caltech in Pasadena. California. The Voyager missions are a part of the NASA Heliophysics System Observatory, sponsored by the Heliophysics Division of the Science Mission Directorate in Washington. Image: NASA

On March 5, 1979, it performed a Jupiter flyby. Saturn flyby followed on November 12, 1980.

Voyager 1 performed its last flyby at 880,440 km (547080.052 miles) from Saturn’s moon Hyperion on November 13, 1980, and its solar system exploration phase has ended.

Voyager 1 in deep space
NASA’s Voyager 1 spacecraft, shown in this illustration, became the first spacecraft in interstellar space on August 25, 2012. Image credit: NASA/JPL-Caltech

After completing its primary mission, Voyager 1 was commanded by NASA to turn its camera around and take a photograph of Earth across a great expanse of space, at the request of Carl Sagan. On February 14, 1990, it took probably the most iconic photo of Earth, dubbed the “Pale blue dot“, from a record distance of about 6 billion kilometers (3.7 billion miles, 40 AU (see notes 1) from Earth.

Then, almost 35 years after its launch, on August 25, 2012, Voyager 1 crossed the heliopause, the theoretical boundary of our solar system where the Sun’s solar wind is stopped by the interstellar medium, and became the first spacecraft in interstellar space.

Its twin, Voyager 2 crossed the heliopause into interstellar space on November 5, 2018.

Video: Voyager 1 reaches interstellar space

The video below, published by the NASA Jet Propulsion Laboratory channel, discusses Voyager 1’s historic milestone, becoming the first spacecraft in interstellar space.

After decades of exploration, Voyager 1 reaches a historic milestone for mankind–interstellar space. Learn how the team discovered the craft had reached the space between the stars.

August 20 in Science, Technology, Astronomy, and Space Exploration history

Notes

  1. The astronomical unit (AU) is a unit of length, roughly the distance from Earth to the Sun. Since 2012 it has been defined as exactly 149,597,870,700 meters or about 150 million kilometers (93 million miles).

Sources

M. Özgür Nevres

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