On this day, September 5th, exactly 48 years are marked since the historic moment when NASA's space probe Voyager 1 began its epic journey from Cape Canaveral in Florida. Launched in 1977, this spacecraft, along with its twin Voyager 2, had the primary mission of exploring the gas giants of our system, Jupiter and Saturn. Almost half a century later, both probes have not only exceeded all expectations but are also still actively exploring, now in the distant and unexplored expanses of interstellar space, sending invaluable data back to Earth. On the occasion of this significant anniversary, NASA's Jet Propulsion Laboratory (JPL) released an archival recording of a press conference held on June 6, 1990. This event marked the formal conclusion of the mission's planetary explorations and presented the world with one of the most famous sights in the history of astronomy – the "Family Portrait of the Solar System".

Portrait of the Solar System: A View from a Cosmic Distance

The aforementioned press conference was a moment to remember. The mission's leading scientists, led by longtime project scientist Ed Stone, presented to the public a mosaic composed of 60 individual images captured by Voyager 1 on February 14, 1990. At that moment, the probe was at an incredible distance of about 6 billion kilometers from the Sun, far beyond the orbit of what was then the most distant known planet, Neptune. From this unique vantage point, Voyager 1 turned its cameras toward the inner system and captured a series of photographs that were then stitched together into a panoramic view. This "Family Portrait" shows six of the eight planets of the Solar System: Neptune, Uranus, Saturn, Jupiter, Earth, and Venus. Each of these worlds appears in the photograph as just a tiny dot of light, no larger than a single pixel, scattered in the vast darkness of space.

Mercury was too close to the Sun to be photographed without damaging the cameras, while Mars was obscured by scattered sunlight. Pluto, which still had the status of a planet at the time, was too small and too dim to be detected. But it was this very perspective, which reduces our world and neighboring planets to mere points of light, that provided a powerful lesson about our place in the universe.

Pale Blue Dot: Our Home as a Speck of Dust

Among these tiny dots, one had special meaning. At the conference, Voyager science team member and celebrated scientist and communicator Carl Sagan presented the image of Earth, caught in a ray of scattered sunlight. He called it the "Pale Blue Dot" and shared a few sentences that would later become the foundation of his famous essay about that image, an essay that deeply reflects on the fragility and uniqueness of our planet.

"We live here – on a blue dot," said Sagan. "This is where everyone you know, everyone you've heard of, and every human being who ever was, lived out their lives. It is a very small stage in a vast cosmic arena. And again, speaking only for myself, I think this perspective underscores our responsibility to preserve and cherish that pale blue dot, the only home we have." Those words resonated around the world and transformed a technical photograph into a deeply philosophical and inspiring work, a symbol of human vulnerability and the need for mutual cooperation and the preservation of our only home.

The idea to capture this portrait came from Sagan himself, who had insisted for years that Voyager's cameras, before being permanently shut down to save energy for the long interstellar journey, be turned one last time toward home. After these historic images were taken, the cameras on Voyager 1 were deactivated to conserve precious energy for the instruments that would measure the characteristics of interstellar space.

The Grand Tour: Discoveries That Changed Science

Although Voyager 1 was launched two weeks after its twin, Voyager 2, both probes performed a spectacular "Grand Tour" through the outer Solar System. Their primary mission included close flybys of Jupiter and Saturn, as well as some of their largest moons. Although they were not the first spacecraft to visit these gas giants, the discoveries they made were revolutionary. Voyager 1 discovered volcanic activity on Jupiter's moon Io, the first such activity observed outside of Earth, and confirmed the existence of a thin ring around Jupiter itself. At Saturn, the probes provided incredibly detailed images of its rings, revealing complex structures like braids, waves, and new, smaller moons that act as "shepherds" for the rings.

Voyager 2 continued its journey, taking advantage of a rare planetary alignment that occurs once every 176 years, and in 1986 it flew by Uranus, and in 1989, by Neptune. This extended mission brought crucial knowledge about the ice giants. To this day, Voyager 2 remains the only space probe to have visited Uranus and Neptune. It discovered new moons and rings around both planets, measured their unusual magnetic fields, and recorded strong winds on Neptune, the fastest in the Solar System. At the aforementioned 1990 conference, Ed Stone briefly presented these and many other discoveries, but also looked towards the future – towards the interstellar mission that had already begun.

Interstellar Mission: In Search of the Boundary

The primary goal of the new phase of the mission, named the Voyager Interstellar Mission (VIM), was to find the boundary of the heliosphere. The heliosphere is a vast "bubble" created by the Sun with its solar wind, a stream of charged particles and magnetic fields. This bubble protects our Solar System from most of the high-energy cosmic rays coming from interstellar space. At that time, the distance to this boundary, known as the heliopause, was a complete unknown and could not be detected by telescopes from Earth.

"The space between the stars, interstellar space, is filled with a very dilute gas that we call the interstellar medium, and each star blows a bubble in that gas," Stone explained at the conference. "We don't know how big the Sun's bubble is... The boundary of this bubble could be 100 times farther than the distance of the Earth from the Sun. Nobody knows!"

It turned out that Stone's estimate was quite accurate, although the heliosphere was even larger. At the time the interstellar mission began, Voyager 1 was at a distance of about 40 astronomical units (AU), while Voyager 2 was at 31 AU (one AU is the average distance of the Earth from the Sun). The long journey paid off. Voyager 1 finally exited the heliosphere and entered interstellar space in August 2012, at a distance of about 122 AU, or 18 billion kilometers from the Sun. Voyager 2, traveling slower and in a different direction, crossed the same boundary in November 2018 at a distance of about 119 AU. The probes also discovered that the heliosphere blocks about two-thirds of the cosmic rays present in the nearby interstellar space, confirming its crucial protective role.

The Voyagers Today: Messengers of Humanity in the Eternal Darkness

Today, Voyager 1 and 2 are at distances of approximately 25 billion and 21 billion kilometers from Earth, respectively, and continue to move away at a speed of over 15 kilometers per second. They are the most distant objects ever created by humanity. Although their power, which they get from radioisotope thermoelectric generators, is slowly fading, scientists expect that at least some of their instruments will continue to operate until about 2025 or even longer. These tireless explorers continue to send data about magnetic fields, cosmic rays, and plasma in the unexplored medium between the stars. Every signal they send travels for more than 22 hours to reach the antennas of NASA's Deep Space Network on Earth. They are our first true messengers in the galaxy, carrying with them the "Golden Record" – a message in a bottle cast into the cosmic ocean, containing sounds and images from Earth, intended for any extraterrestrial civilization that might encounter it in the distant, distant future.