In November 2018, NASA’s Voyager 2 space probe became the second object launched from Earth to exit the outer boundary of the solar system — about 11 billion miles away — and enter the realm of interstellar space. Its twin craft, Voyager 1, was the first, crossing the barrier in 2012. Since their launches in 1977, the spacecrafts have taken beautiful fly-by images of Jupiter, Saturn, Uranus and Neptune, along with their moons. New papers published in Nature Astronomy look into the differing properties of the environments inside and outside of our solar system. The findings confirm that our solar system has a clearly defined boundary — the heliopause. Beyond the heliopause there is a sharp drop in solar wind particles, and high-energy galactic cosmic rays, which originate from galactic systems in interstellar space, dominate.
Both Voyager crafts will eventually exhaust the power necessary for them to collect data and transmit it back to Earth, likely in the next decade. However, they will continue traveling through the cosmos, fueled by inertia. They will speed through space that we currently only know about through data from instrumentation on Earth, inhabiting the heavens that have stirred our imaginations for as long as we’ve looked up at the night sky. The Voyager probes are equally amazing and unsettling, expanding our understanding of outer space while presenting a unique perspective on life, death and fate.
NASA initiated The Voyager Program project during the Space Race frenzy, an outgrowth of the Cold War that led to tremendous technological advances and an increased curiosity in the universe beyond our Earth. The Voyager probes are the perfect examples of humans’ insatiable quest for increased knowledge. With every new bit of daily information on the interstellar magnetic field, the boundaries of our human knowledge are pushed outward. The insights gleaned from the Voyager Program may not be closely relevant to the health and social issues that immediately affect our daily lives, but it is amazing to see humans using what we already know to create new ways to learn even more about this universe.
But there will be a time when Voyager 1 and Voyager 2 no longer contribute to the expansion of our knowledge. Voyager 1 is already using backup thrusters to keep its antennae pointed toward Earth, and NASA predicts its instrumentation, and that of Voyager 2, will lose all instrument function by about 2025. After that, they will face the same fate as the Pioneer probes. Pioneer 10 and Pioneer 11 were launched in the early 1970s and were the first spacecraft to encounter Jupiter and Saturn, respectively; they no longer have any communication with Earth. Pioneer 11 has already escaped the solar system, and Pioneer 10 is predicted to follow suit.
I view the moment a probe stops functioning as the moment of “death” of the probe. What was once a silent explorer cutting through vast space will succumb to its entropy and serve no further purpose. Unlike the terrestrial death of a biological being or a technological work, however, there is no rest for the probes that die. NASA believes that Voyager 2 may continue to zip through the cosmos eternally, traveling billions upon billions of miles for as long as the existence of time itself.
The universe naturally creates countless objects that will forever remain flying through space. These objects were never given life to begin with and therefore will never die. Others, such as stars, eventually undergo end-of-life processes that see them quietly fade away or become something different from what they originally were. The Voyager probes, in contrast, were created by humans from materials provided by the universe. They were built with missions and survived to fulfill them, but their deaths lack closure because they will continue to wander the darkness indefinitely, existing without purpose. What is defeating about the impending deaths of Voyager 1 and Voyager 2 is that we will know of their death the moment it occurs, but we will not be able to examine what failed mechanically, and we will not be able to celebrate and retire them.
This column is not a knock on the Voyager Program or to the aspirations of those who wish to explore the unknown. It is rather a musing on the fates of objects, including the Voyager 2 space probe, that may join some of the first human-made creations to have no limits on how far and how long they travel. When Voyager 2 completely ceases to function, it will indeed become nothing but a voyager – traveling, and nothing else.
Dipra Debnath can be reached at dipra@umich.edu.