We’re leaving the solar system.
How’s that sound for a vacation? It’s certainly not something you do on the spur of the moment, and it’s a trip the Voyager spacecrafts have been on for 35 years. Launched in the late 1970s by NASA, these two ambassadors for humanity are laden with objects meant to give extraterrestrial intelligence a taste of life on Earth, and have finally reached the edge of our solar system.
Voyager 1 is traveling slightly ahead of fellow explorer Voyager 2, approximately 11 billion miles from Earth and continuing the journey at a rate of 8 miles per second. As they travel, the Voyagers transmit close-up images of planets and stars along the trails they’re blazing through space – including the first-ever close-ups of Jupiter, Saturn, Uranus and Neptune. Each craft is well-stocked with instruments to gather information about the unfamiliar territory they’re entering, as well as a gold-plated copper disk containing sounds and images that demonstrate a wide variety of human experience and knowledge.
Assuming intelligent life does find the disk – and is able to decode it – the first specimen of humanity they will encounter is Ann Druyan, an author, television producer and the third wife of astronomer Dr. Carl Sagan. The two met while working on the Voyager project, where Ms. Druyan was the creative director of the Voyager Interstellar Message Project, responsible for assembling the contents of the aforementioned disk.
Included in the greeting package are greetings in 55 languages and the song of the humpback whale, but also a more personal gift from Ms. Druyan – a recording of her brain waves as she thought about the moment she agreed to marry Dr. Sagan.
Three signs are necessary before scientists will be able to confirm the spacecrafts have left the solar system: dropping of the solar wind from our sun, increased levels of cosmic rays and an alteration in the magnetic field surrounding the Voyagers.
Dr. Ed Stone, former director of NASA’s Jet Propulsion Laboratory and project scientist for the Voyager mission, explains. “The solar wind goes out at a million miles an hour from the sun. It gets thinner and thinner, and at some point it reaches the wind from the interstellar space from the supernova explosions and there is a boundary between the two.” Data from the instruments on Voyager 1 shows that the solar wind has dropped 90 percent from the level it has held for the last seven years, and the levels of cosmic rays are unprecedentedly high.
The ships have enough power in reserve to last until 2020, at which point they will switch to “powersaving” mode, and continue their mission for several decades – assuming they survive the transition to as-yet unexplored realms. After leaving our solar system, the Voyagers will encounter a particle wind generated by supernova explosions millions of light-years away. Scientists are uncertain how long the spacecrafts will survive their journey, but one thing is certain: the Voyagers have provided scientists with an amazing range of new data, and are a shining example of what can be accomplished when humanity turns its ingenuity to the stars.