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  • They are part of an ancient quest.

  • To push beyond our boundaries, to see what lies beyond the horizon.

  • Now tens of billions of kilometers from Earth, two spacecraft are streaking out into the void.

  • What will we learn about the Galaxy, the Universe, and ourselves from Voyager’s epic Journey

  • to the stars?

  • December 19, 1972. The splashdown of the Apollo 17 crew capsule marked the end of the golden

  • age of manned spaceflight.

  • The Mercury, Gemini, and Apollo programs had proven that we could send people into space,

  • to orbit the Earth, fly out beyond our planet, then land on the moon and walk among its ancient

  • craters.

  • The collective will to send people beyond our planet faded in times of economic uncertainty,

  • war, and shifting priorities.

  • And yet, just five years after Apollo ended, scientists launched a new vision that was

  • just as profound and even more far-reaching.

  • We knew we were on a journey of discovery when we launched the Voyager spacecraft, but

  • we had no idea how much there was to discover.

  • We had a sense that we knew what it felt like to be Magellan or Columbus

  • It didn’t all go smoothly. Early computer problems threatened to doom Voyager 2. Then

  • its radio receiver failed, forcing engineers to use a back up.

  • Now, after more than three and a half decades of successful operations, the twin spacecraft

  • are sending back information on their flight into interstellar space.

  • Along the way, they have revealed a solar system rich beyond our imagining.

  • Time after time we were surprised by seeing things that we had not expected or even imagined:

  • volcanoes erupting from the moon, Io, the possibility of a liquid water ocean under

  • the icy crust of Europa, Titan, where we found an atmosphere, Uranussmall moon, Miranda,

  • which had one of the most complex geologic surfaces weve seen. Even at Neptune, 40

  • degrees above absolute zero, even there, there were geysers erupting.

  • It’s the only spacecraft that has gone by Uranus. It’s the only spacecraft that has

  • gone by Neptune. Everything we know about those planets, we know from Voyager.

  • To see those first pictures coming in from the outer solar system, for the first time,

  • what had been a point of light in the sky was a place.

  • The journey was made possible by a rare alignment of the planets, a configuration that occurs

  • only once every 176 years.

  • That enabled the craft to go from planet to planet, accelerating as they entered the gravitational

  • field of one, then flying out to the next.

  • The Voyagers carried a battery of scientific equipment to collect data on the unknown worlds

  • in their path. That included a pair of vidicom cameras, and a data transfer rate slower than

  • a dialup modem.

  • They are primitive by today’s standards, but that didn’t stop them from returning

  • a flurry of discoveries. On Jupiter’s moon Io, Voyager’s cameras spotted nine erupting

  • volcanoes.

  • They documented volcanic plumes reaching 300 kilometers into the atmosphere, at velocities

  • of one kilometer every second.

  • Almost two years later, on November 12, 1980, Voyager 1 sailed down to within 124,000 kilometers

  • of Saturn’s cloud-tops. That’s one-third the distance between Earth and the moon.

  • It found that Saturn’s atmosphere is almost entirely hydrogen and helium. It is the only

  • planet in our solar system that is less dense than water.

  • One year earlier, Pioneer 11 had detected a thick, gaseous atmosphere on Saturn’s

  • large moon, Titan. Scientists decided to send Voyager 1 to follow up.

  • It sent back clues to one of the most fascinating bodies in the solar system.

  • Titan proved to be the only object in the solar system, other than Earth, with stable

  • bodies of surface liquid. Not water, but vast lakes of liquid methane.

  • Scientists could have chosen to send Voyager 1 out to Pluto. But Titan was more promising

  • scientifically.

  • But that meant its grand tour of the outer planets was over. Voyager 1 headed north,

  • above the plane of the solar system.

  • Five years later, and over a billion and a half kilometers beyond Saturn, Voyager 2 reached

  • Uranus.

  • Like all the other planets, Uranus spins like a top. But Voyager 2 found that it’s actually

  • tipped on its side. Its magnetic field reaches out in a bizarre corkscrew tail, millions

  • of kilometers into space.

  • Voyager 2 discovered two new rings; thin, dark bands of ice, rock, and dust with particles

  • the size of a fist.

  • Although the craft discovered 10 new Uranian moons, the most eagerly anticipated event

  • was a close encounter with Miranda, perhaps the most bizarre object in our solar system.

  • Close-ups revealed a strange and wondrous landscape including a canyon 19 kilometers

  • deep.

  • Miranda may have collided with another moon, shattered, and then by the force of its own

  • gravity, slowly reassembled into this chunk of rock and ice.

  • After 12 years on the road, Voyager 2 now sped toward its rendezvous with Neptune.

  • The planet appears blue because methane in its atmosphere absorbs most of the red in

  • the light spectrum.

  • Remarkably, Voyager 2 flew by Neptune only 35 kilometers off its charted course and only

  • 1 second off its scheduled fly-by time.

  • Skimming only 5,000 kilometers above the planet’s north pole, Voyager found Neptune to be a

  • giant ball of melted rock and ice. Cloaked in hydrogen, helium, and methane gasses, its

  • atmosphere is whipped by winds of 1,000 kilometers per hour.

  • Flying in closer than any spacecraft has come to one of the outer planets, Voyager 2 discovered

  • at least four complete rings of ice and rock, six new moons, and a great dark spot; a hurricane

  • the size of Earth raging in Neptune’s southern hemisphere.

  • The storm circles the planet every 18 hours, and rotates around its own axis every 16 days.

  • Oddly, the largest of Neptune’s 8 moons, Triton, orbits in the opposite direction to

  • the planet’s spin.

  • Triton was likely an independent object in orbit around the sun, until it was captured

  • by Neptune’s gravity.

  • Pocked with impact craters and glazed with methane and nitrogen ice, Triton is the coldest

  • known object in the Solar System, at minus 240 degrees Celsius.

  • On its surface, scientists saw jagged mountains, high cliffs, and frozen lakes.

  • The most bizarre discovery was the presence of icy geysers with plumes reaching 160 kilometers

  • downwind.

  • Leaving Neptune, Voyager 2 snapped one of the most remarkable pictures ever taken.

  • Neptune and its cold moon Triton, framed by the dim light of the Sun.

  • Several years earlier, the Pioneer spacecraft carried a plaque illustrating the spin state

  • of a hydrogen atom, a man and woman set against an outline of the spacecraft, and the position

  • of the Sun relative to 14 prominent pulsars.

  • The Voyagers brought their own message in a bottle: a disk encoded with images of life

  • on Earth, greetings in 55 languages, a selection of music, messages, and natural sounds.

  • And here was this Noah’s Ark of human culture that was being sent to the outer planets,

  • and then beyond to wander in the interstellar darkness for a billion years. On Valentine’s Day 1990,

  • Voyager 1 looked homeward. And what did it find? Not the frame-filling Apollo Earth,

  • but instead, that one-pixel Earth. That’s here. That’s home.

  • Thirteen years after launch, the Voyager craft finally began their journey into the galaxy

  • at large.

  • They run on plutonium-powered Radioisotope Thermoelectric Generators, a standard set

  • up for NASA deep space missions. Because even these systems don’t last forever, scientists

  • have had to shut down Voyager’s instruments one by one.

  • Among the most valuable remaining sensors are magnetometers that can read magnetic fields

  • that constantly sculpt the outer solar system.

  • This region is the outer edge of a bubble formed by the sun’s magnetic field and the

  • solar wind.

  • Tonight were going to be getting the data back from a magnetometer roll calibration

  • maneuver, and that maneuver actually happened on the Voyager 1 spacecraft over 16 hours

  • ago, and the data is finally making it back to the earth. What were doing is a roll

  • about this high-gain antenna, and so if the high-gain antenna here is pointed out toward

  • earth were going to be rolling the spacecraft along that high-gain antenna. That roll is

  • done so that we can calibrate the instrument so that we know what magnetic field belongs

  • to the sun and what component belongs to the actual spacecraft.

  • Theyre very near the edge of the bubble the sun creates around itself called the Heliosphere.

  • Were getting very close to the boundary. We don’t know how close because no spacecraft

  • has ever been there before, but it could be another few months, it could be another few

  • years, but it’s probably not much longer than that. We travel a billion miles every

  • three years.

  • You can’t see the bubble the sun creates around itself because it’s invisible, but

  • we can see an analog of it in a sink. If we turn the water on very fast and look at the

  • bottom of the sink, we see that near where the water hits the bottom of the sink, it’s

  • flowing very fast radially outward in all directions, and getting thinner until it abruptly

  • slows down in this thick region, and turns around and flows down the drain. The two Voyager

  • spacecraft are both in this thick region in our heliosphere where the wind has slowed

  • down and is starting to go down the tail of the heliosphere. And eventually, in hopefully

  • not too many more years, Voyager 1 will leave this thick region and enter interstellar space.

  • We have a 20-watt transmitter on the spacecraft transmitting over 11 billion miles away, and

  • so it comes in very slowly. But every bit left that spacecraft over 16 hours ago and

  • every bit is telling us something new that we haven’t known before.

  • As the solar wind travels out from the sun, it pushes against the galactic medium and

  • abruptly slows down in a region called the Termination shock. Outside this is the Heliosheath,

  • where the sun’s magnetic field is bent back by the interstellar wind.

  • The sun’s magnetic field spins in opposite directions on the north and south poles, creating

  • a sheet where the two spins meet. This sheet gently ripples as it travels outward. When

  • this sheet reaches the termination shock, it starts to compress like water waves hitting

  • a wall.

  • The voyager spacecraft have now found that these stacked up ripples of magnetic field

  • form smaller bubbles, shown here as a computer simulation.

  • The discovery of this frothy character changes our understanding of how extremely fast moving

  • particles, called cosmic rays, enter our solar system.

  • When they arrive at this region, they slowly move from bubble to bubble until they can

  • reach smooth magnetic field lines and follow them toward the sun.

  • Recently, the twin Voyagers began their transition into interstellar space.

  • Voyager today is headed for the edge of interstellar space. That’s the space between stars and

  • it’s filled with material that has been injected by the explosion of stars, matter

  • which came from a particular direction, creating a wind which has shaped the bubble in which

  • the solar system is surrounded.

  • Since July of 2012, the solar wind has decreased, while the galactic wind has sped up.

  • That places the craft in what scientists call themagnetic highway,” where the alignment

  • of magnetic fields allows particles from the sun to escape, and particles from the galaxy

  • to pour in.

  • When either one reports a complete change in the direction of the magnetic field, that’s

  • when scientists will know that it has finally exited the solar system.

  • Meanwhile, they are delivering a whole new view of the galaxy in ultraviolet light. From

  • Earth, this light is normally blocked by the haze of particles at the edge of the solar

  • system.

  • Scientists are able to capture this light from other galaxies because their wavelength

  • has been shifted slightly by their journey through space.

  • Because ultraviolet light reveals the location of vigorous star birth, it is providing a

  • new window on the evolution of our galaxy.

  • The Voyagers will keep sending back this and other valuable data sets until their power

  • begins to run out. Theyll finally go dead around the year 2025.

  • Voyager 2 will be heading south toward the constellation Sagittarius. Travelling at 16

  • kilometers per second, it is expected to pass 4 light years from Sirius, the brightest star

  • in the heavens, 290,000 years from now.

  • Its twin will continue on a northward track to a relatively empty region of our solar

  • neighborhood.

  • They will become silent emissaries from planet earth, symbols of our boundless curiosity

  • and aspiration.

  • In the words of Carl Sagan:

  • These Spacecraft have taught us about the wonders of other worlds, about the uniqueness

  • and fragility of our own, about beginnings and ends. They have given us access to most

  • of the solar system, both in extent and in mass. They are the ships that first explored

  • what may be homelands of our remote descendants.”

  • At the same time, Voyager’s journey into the vast and forbidding oceans of interstellar

  • space reminds us how closely our fate is tied to our home planet.

  • The twin craft will wander the galaxy undisturbed for millions, even billions of years. They

  • will endure long after everything man has built has crumbled to dust.

  • Compared to Voyager, we are living on borrowed time, for mammalian species only last on average

  • about a million years.

  • Our ability to follow them into deep space will take a new perspective on time and distance,

  • beyond the short years and decades of human activities.

  • Well continue to track Voyager’s slow but remarkable journey, while our civilizations

  • and our planet change and evolve in the cosmic blink of an eye.

They are part of an ancient quest.

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