At 11.6 billion miles (18.7 billion kilometers) away from Earth (as of September 12, 2013), the Voyager 1 spacecraft is the most distant human-made object. It passed the previous record holder, Pioneer 10 in 1998.
Voyager 1 has entered interstellar space. The NASA spacecraft, which rose from Earth on a September morning 36 years ago, has traveled farther than anyone, or anything, in history. Now Voyager 1 is in the space between the stars. How did Voyager 1 get there? How do we know and where is it going?
Voyager 2 launched on Aug. 20, 1977, about two weeks before the Sept. 5 launch of Voyager 1. Why the reversal of order? The two were sent on different trajectories, and Voyager 1 was put on a path to reach its planetary targets, Jupiter and Saturn, ahead of Voyager 2.
Voyager 1 and Voyager 2 have 69.63 kilobytes of memory each. For comparison, an iPhone 5 with 16 gigabytes of memory has about 240,000 times the memory of a Voyager spacecraft
Both Voyagers communicate to Earth through NASA’s Deep Space Network. A signal from the ground, traveling at the speed of light, takes 17 hours one way to reach Voyager 1, and 14 hours one way to reach Voyager 2.
It took 35 years to reach interstellar space, but it will take 40,000 years for Voyager 1 to be closer to the star nearest us, AC +79 3888 than our sun. Alpha Centauri is the closest star to our own right now, but because stars are moving, Voyager 1 will actually get within 1.7 light years of AC +79 3888 (aka Gliese 445) in 40,000 years.
Voyager carries sounds from Earth on a golden phonograph record. A team led by the late astronomer Carl Sagan selected natural sounds, greetings in 55 languages and music from different cultures to serve as a message to any life form that might someday meet our spacecraft. The musical selections include Bach, Beethoven and Chuck Berry.
Voyager 1 first detected the increased pressure of interstellar space on the heliosphere, the bubble of charged particles surrounding the sun that reaches far beyond the outer planets, in 2004. Scientists then ramped up their search for evidence of the spacecraft’s interstellar arrival, knowing the data analysis and interpretation could take months or years.
Voyager 1 does not have a working plasma sensor, so scientists needed a different way to measure the spacecraft’s plasma environment to make a definitive determination of its location. A coronal mass ejection, or a massive burst of solar wind and magnetic fields, that erupted from the sun in March 2012 provided scientists the data they needed. When this unexpected gift from the sun eventually arrived at Voyager 1’s location 13 months later, in April 2013, the plasma around the spacecraft began to vibrate like a violin string. On April 9, Voyager 1’s plasma wave instrument detected the movement. The pitch of the oscillations helped scientists determine the density of the plasma. The particular oscillations meant the spacecraft was bathed in plasma more than 40 times denser than what they had encountered in the outer layer of the heliosphere. Density of this sort is to be expected in interstellar space
