Voyager 2: It’ll Spend Eternity Cruising Space
In a billion years, when drifting continents have reshaped Earth’s face and humans are extinct or changed by evolution, Voyager 2 will still be cruising the stars.
“It’s mind-boggling. We’re actually going out to the stars,” said Bruce Brymer, Voyager’s lead mission controller at NASA’s Jet Propulsion Laboratory in Pasadena. “This spacecraft is going to outlive us. It’s going to be out there forever.”
In August, Voyager 2 swept past Neptune and its icy volcanic moon Triton--the last planetary exploration in an incredible 12-year journey that also took the spacecraft past Jupiter, Saturn, Uranus and more than 50 moons.
Now, Voyager 2 is speeding into the loneliest part of its trek: the Voyager Interstellar Mission. With Voyager 1, it will study the sun’s magnetic field, solar wind and ultraviolet light from distant stars and galaxies.
Like Pioneers 10 and 11 and Voyager 1, which explored Jupiter and Saturn, Voyager 2 also will search for the edge of the solar system.
The Voyagers are expected to return information to Earth until about 2015 or 2020. Contact eventually will be cut off by some malfunction, by exhaustion of the probes’ plutonium power generators, or when their thruster fuel runs out, leaving them unable to point antennas at Earth.
Then, the robot explorers will pass among the stars, each carrying a 12-inch copper record of sounds and sights from Earth in case they are found by a spacefaring civilization. “Hopefully they will understand our peaceful and humble attempt at knowing and exploring the great unknown,” Brymer said.
For now, Voyager 2’s work is more mundane.
“The interstellar mission is sort of anticlimactic. There’s no real drama expected. We’re suffering from the blues a little bit,” he said. “It’s almost like postpartum depression. We’ve gone through such highs with the spacecraft. There’s a great sense of melancholy now. It’s like none I’ve sensed before.”
Voyager 2’s encounter with Neptune officially ends Oct. 2, when it will be 34.7 million miles past the planet, going 37,337 m.p.h. It will be 2.83 billion miles from Earth, and will have traveled 4.46 billion miles since 1977.
Until December, Voyager 2 occasionally will glance at Neptune and dark space to improve the accuracy of observations its cameras and instruments made during the Neptune flyby, said Voyager project manager Norm Haynes.
Pictures of empty space let engineers measure how much sunlight reflects off Voyager into its cameras. A computer can subtract the light from Voyager’s Neptune and Triton photographs, producing clearer prints, Haynes said.
In April, most of the planets will be positioned for one of the Voyagers to take photographs for assembly into a single picture of the solar system. “The planets are small and there’s lots of dark space out there,” he said. “Maybe it will give people a better impression of the vastness of things.”
Then engineers will turn off Voyager 2’s TV cameras and its infrared and visible light sensors.
Sensors Already at Work
Voyager’s Interstellar Mission officially starts Jan. 1, but the spacecraft already is using its remaining sensors to make the kind of measurements it will continue to collect for years. Ultraviolet light and cosmic ray sensors study distant galaxies and stars, and also black holes and pulsars--remnants of stars that died in fiery supernova explosions.
Both Voyagers also will keep measuring magnetic fields, electrically charged particles that make up solar wind, and waves in that wind.
If the Voyagers and Pioneers survive, one or more of them may detect the “heliopause,” where solar wind yields to interstellar wind 5 billion to 14 billion miles from the sun. Many scientists consider it the edge of the solar system.
By about 2020, the Voyagers will lose contact with Earth.
“My electrical energy is fading, and I am feeling old and useless,” says Voyager 2’s imaginary voice in “The Voyager Neptune Travel Guide,” a National Aeronautics and Space Administration publication. “The planet which gave me life said goodby. I will no longer hear its voice, nor it my heartbeat.”
Then, Voyager will approach the stars, passing them like distant beacons in an incredible void.
In the year 20391, Voyager will pass within 3.21 light years, 18.9 trillion miles, of Proxima Centauri, the nearest star. About 24,000 years from now, it should pass through the Oort Cloud, a vast spherical cloud of comets that other scientists consider the true edge of the solar system.
“Then Voyager makes for the open sea of interstellar space, free of the sun’s gravity and wandering forever in the Milky Way galaxy, going around the center of the galaxy once every quarter-billion years,” said Cornell University astronomer Carl Sagan.
NASA estimates that in the year 40176, Voyager 2 will fly 1.65 light years from Ross 248--the first time it will be closer to another star than to the sun, which will be 1.99 light years from Voyager.
Near Sirius in Year 296036
In the year 296036, Voyager 2 will make its closest approach to Sirius, the brightest star visible from Earth.
Deep space is benign, so dust and cosmic rays will erode Voyager 2 extraordinarily slowly.
In a billion or more years, Sagan said, “there will be no more humans because we’ll be extinct or we’ll be somebody else. There will be no human artifacts left on Earth. Continental drift will completely change what the continents look like.
“But this brave spacecraft will be there, a surviving artifact of our species and our times.”
Perhaps one day, aliens in a starship may find one of the Voyagers, then play the copper record.
They will hear greetings in 60 languages from Chinese to Welsh to Urdu, including a 7-year-old boy offering salutations from Earth’s children.
There also is the music of many cultures, from Chuck Berry’s rock ‘n’ roll to Mozart, Bach and Beethoven.
The aliens will listen to the sounds of surf, wind, rain and thunder; croaking frogs and laughing hyenas; a train, a truck, a jet and a rocket; a baby crying and lovers kissing.
The record also holds 115 electronically encoded photographs or diagrams showing humans, the Earth and other planets, human chromosomes, a fetus, the Golden Gate, the Grand Tetons and the Great Wall of China.
And the extraterrestrials will read a message written July 16, 1977, by Jimmy Carter, then President of a nation on a little planet that, two months later, dared to send a bit of itself to the stars:
“This is a present from a small distant world, a token of our sounds, our science, our images, our music, our thoughts and our feelings.
“We are attempting to survive our time so we may live into yours. We hope someday, having solved the problems we face, to join a community of galactic civilizations. This record represents our hope and our determination, and our good will in a vast and awesome universe.”
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