NASA’s Voyager 1 and Voyager 2 spacecraft, launched in 1977, have ventured further from Earth than any manmade objects, now traveling over 12 billion miles from our planet. As Voyager 1 approaches a distance of one light-day from Earth by the end of this month, it has encountered a region described as a “wall of fire,” with temperatures soaring to an astonishing 90,000 degrees Fahrenheit. This discovery sheds light on the extreme conditions at the outer boundaries of our solar system.
Both spacecraft originally set out to explore the outer planets, but their mission has evolved into an unprecedented journey into the interstellar medium. Operating at the limits of technology, NASA has had to periodically shut down instruments and reactivate systems that have remained dormant for decades to keep the spacecraft functional. Despite these challenges, they continue to provide valuable data about the solar system’s edge.
Understanding the Heliopause
The region where Voyager 1 and 2 encountered extreme heat is known as the heliopause, which marks the boundary between our solar system and interstellar space. The heliosphere, a bubble formed by solar wind—protons and electrons emitted from the Sun—creates this boundary. Inside the heliosphere lies our solar system, while the exterior consists of the interstellar medium, composed of gas, dust, and charged particles.
Scientists have debated the precise borders of the solar system. Some argue that once one passes the planet Neptune, they have entered interstellar space, while others define the boundary based on the gravitational pull of the Sun. Currently, the prevailing perspective is that the solar system concludes beyond the Sun’s magnetic influence. The Voyager missions have provided crucial insights into this phenomenon, confirming the existence of solar winds and their impact on the heliosphere.
New Discoveries at the Edge
In 2012, Voyager 1 became the first spacecraft to cross the heliopause, followed by Voyager 2 in 2018. Their different arrival times highlight the non-spherical nature of the heliosphere, which scientists had theorized could expand and contract based on solar activity. The shape of the heliosphere resembles a teardrop, creating a bow shock as our solar system moves through the interstellar medium, similar to the wake left by a boat in water or a supersonic aircraft.
The extreme temperatures encountered by both spacecraft, ranging from 54,000 to 90,000 degrees Fahrenheit, illustrate the dynamic environment at the solar system’s edge. While these conditions may seem ferocious, once they stabilize, it becomes evident that the Voyagers have successfully reached interstellar space. Their continued exploration offers invaluable data that enhances our understanding of the universe beyond our solar system.
As these pioneering spacecraft push the boundaries of human exploration, NASA remains committed to analyzing the information gathered by Voyager 1 and Voyager 2. Their legacy as ambassadors for humanity continues to unfold, revealing the mysteries of the cosmos and expanding our knowledge of the vast universe that lies beyond our reach.
