Press play above, and then come back down here.
The Voyager 1 spacecraft, launched 34 years ago, is about to cross into the great unknown — currently poised on the edge of interstellar space, it will soon leave our solar system forever. The song above is “Dark Was the Night, Cold Was the Ground” by Blind Willie Johnson. It was included on the Voyager Golden Record as an expression of human loneliness (awesome), and it’s a fitting soundtrack for Voyager on this endless, solitary journey.
Voyager was first conceived as an extension of the Mariner program, which would address Gary Flandro’s Planetary Grand Tour concept — an idea to launch a probe that would use gravitational slingshots to traverse the Solar System, and collect data from each planet as it went by. Eventually, the requirements of Voyager became distinct enough from Mariner that it was spun off as it’s own program. Voyager I was launched after Voyager II, but it’s trajectory is more directly away from the sun, and faster, so it is currently the most distant man-made object in the solar system.
According to recent data received from the craft, scientists believe that it’s nearing the heliopause, which is the point at which the solar wind meets the interstellar medium of greater space, and is considered the boundary of interstellar space. From BBC News:
The Nasa mission, which launched from Earth in 1977, could leave our Solar System at any time.
It is now detecting a sharp rise in the number of high-energy particles hitting it from distant exploded stars.
The observation was predicted, and is another indication that Voyager will soon reach its historic goal.
“The laws of physics say that someday Voyager will become the first human-made object to enter interstellar space, but we still do not know exactly when that someday will be,” Ed Stone, the Voyager project scientist at the California Institute of Technology in Pasadena, said in a Nasa statement.
“The latest data indicate that we are clearly in a new region where things are changing more quickly. It is very exciting. We are approaching the Solar System’s frontier.”
Voyager 1 is travelling at about 17 km per second (38,000 mph), and is almost 18 billion km (11 billion miles) from Earth.
The vast separation means a signal from the probe takes more than 16 and a half hours to arrive at Nasa’s receiving network.
In the last three years, Voyager has seen a steady increase in the number of cosmic rays entering its two high-energy telescopes, but in the past month the counts have jumped markedly.
About a month ago, Timothy Ferris wrote this piece in Smithsonian about his anticipation of Voyager’s next big step.
The twin Voyager probes are currently poised on the brink of interstellar space. Both are immersed in the foamy walls of the transparent “heliospheric bubble,” where the solar wind, consisting of particles blown off the Sun, stalls against the stellar winds that permeate the rest of the galaxy. Astronomers don’t know how thick the bubble walls are—that’s for the Voyagers to ascertain—but they expect the probes to burst free and begin reporting from the great beyond within the next three years. This final phase of the probes’ scientific mission should last until around 2020 to 2025, when their plutonium power sources will falter and their radios fall silent.
Thereafter the Voyagers will wander forever among the stars, mute as ghost ships but with stories to tell. Each carries a time capsule, the “Golden Record,” containing information about where, when and by what sort of species they were dispatched. Whether they will ever be found, or by whom, is utterly unknown. In that sense, the probes’ exploratory mission is just beginning.
Having played an incidental role in the mission, as producer of the Golden Record, I attended the first launch, on August 20, 1977—Carl Sagan embracing me and shouting, “We did it!” over the rolling thunder of the Titan-Centaur rocket as it climbed into a blue Florida sky atop a roiling pillar of smoke—and was among the hundreds of journalists who showed up at the Jet Propulsion Laboratory (JPL) outside Los Angeles each time the probes swept by another planet. These “encounters,” as they were called, resembled school reunions, where those of us drawn together by passion or profession witnessed one another’s journeys from young upstarts to senior citizens.
For folks who were involved in building Voyager, it must be exciting to have watched this adventure unfold over the course of 35 years. They will soon be saying goodbye as it drifts out into the cosmos, so for them this must be a strange moment of ‘letting go’.
In fact, it’s a weird moment for all of us — humanity is about to make it’s mark (however small) out there. It’s fun to imagine what sort of creatures may encounter Voyager, and what they’ll think of us when they listen to our mixtape.