Like a young adult pushing off on her own, NASA’s Voyager 1 space probe has left the solar system for the stars beyond. At a distance of about 12 billion miles (19 billion km) from the sun, the spacecraft has become the first human-made object to travel into interstellar space – literally the space between the stars.
Amazing raw footage of Jupiter when Voyager 1 headed for the planet in Feb. 1979
Although the announcement was made today, Voyager 1 has been traveling through plasma in the space between the stars since August 2012. A plasma is a gas that’s been ionized or stripped of its electrons by energetic processes in space. The sun releases plasma in solar storms as do other stars.
Scientists on Earth knew Voyager was in a transitional region, teetering on the edge of the sun’s influence and that of the star, but not until a fortuitous storm on the sun were they certain the probe had finally crossed the border.
Voyager began to feel the increased pressure of interstellar plasma back in 2004 when it detected changes in the outer heliosphere, a vast domain of solar influence extending far beyond the 8 planets. In March 2012 the sun cut loose with a coronal mass ejection or massive burst of solar wind and magnetic fields. When this unexpected gift eventually arrived at Voyager 1’s location 13 months later in April 2013, the plasma around the probe began to vibrate like a plucked violin string. After analyzing the signals, scientists discovered those particular vibrations indicated plasma 40 times denser than the solar variety around Voyager 1 – exactly what was expected for interstellar space.
After review of this event and another weaker one in Nov. 2012, they came to the conclusion that Voyager 1 entered the domain of the stars as early as Aug. 2012.
“We literally jumped out of our seats when we saw these oscillations in our data — they showed us the spacecraft was in an entirely new region, comparable to what was expected in interstellar space, and totally different than in the solar bubble,” said Don Gurnett of the University of Iowa, who led the data analysis.
Voyager is so far away it takes 17 hours for its signal, traveling at the speed of light, to reach the Earth. The signals are very weak – a mere 23 watts or about the same as a kitchen refrigerator light – yet they’re picked up and listened to every day by NASA’s Deep Space Network.
Clip from Star Trek: The Motion Picture featuring “Vger”, the discovery of a Voyager craft by aliens 300 years from now
While there now appears to be no question of Voyager’s transition to interstellar space, it will still feel the effect of the sun’s influence for some time as bubbles of plasma from future solar disturbances barrel through space. No one knows for certain when it will reach interstellar space ruffled only by the mingled winds of alien stars. It’s sister craft, Voyager 2, now 9.5 billion miles (15 billion km) from the sun, will be the next human emissary to the stars.
Voyager 1’s journey may last a billion years or more. As our robotic stand-in, a little bit of me and you get to go along for the long ride.
Picture if you will a brilliant speck of light 15 times brighter than the full moon off to one side of Voyager’s vision. That’s the sun. Now look around and all you see are stars. Lots of them. With no atmosphere to flutter their light, they never twinkle. There’s the familiar band of the Milky Way circling above your head and below. No Earth to get in the way and block the view.
It feels lonely out there, quiet and cold. Our little blue world is such a treasure.