Back in 1977, Voyager 2 was launched 16 days before Voyager 1. Both spacecraft were designed to last five years in order to conduct up-close and personal studies of Jupiter and Saturn.
As the success and longevity of the missions continued, remote reprogramming was used to give the twins greater capabilities. This allowed the mission parameters to change from a two-planet to a four-planet flyby.
Knowing the spacecraft were never destined to return to Earth, each was loaded with a Golden Record of Earth sounds, pictures, and messages in multiple languages.
The Voyager story has inspired generations of scientists and engineers, as well as music, art, and films like Star Trek: The Motion Picture.
And while we’ve not found that either has yet been enhanced by alien tech, the spacecraft and their respective Golden Records could last billions of years. While the twins haven’t been out in space for quite that long, their five-year mission has stretched to 41 years, so far. This makes Voyager 2 the longest running mission of NASA.
Even though Voyager 1 was launched second, the twins were sent on different trajectories, allowing Voyager 1 to enter interstellar space back in 2012.
Interstellar space is the area that lies beyond the Heliosphere. For reference: the outflow of plasma from the sun, also known as solar wind, creates a bubble that envelopes all the planets in our solar system. It is this bubble that is known as the Heliosphere.
The space surrounding Voyager 2 was predominately filled with plasma flowing from the Sun, until recently.
Evidence of this comes from Voyager’s Plasma Science Experiment (PLS), an onboard instrument that uses electrical current of the plasma to detect the temperature, density, speed, pressure, and flux of the solar wind. Since November 5th, Voyager 2 has observed a steep decline in the speed of the solar wind particles making it likely that it has exited the Heliosphere.
And, indeed, NASA confirmed today that Voyager 2 has also entered interstellar space.
“Voyager has a very special place for us in our heliophysics fleet,” said Nicola Fox, director of the Heliophysics Division at NASA Headquarters. “Our studies start at the Sun and extend out to everything the solar wind touches. To have the Voyagers sending back information about the edge of the Sun’s influence, gives us an unprecedented glimpse of truly uncharted territory.”
Although the twins have left the heliosphere, they have no yet left the solar system. Far beyond the planets is an area known as the Oort Cloud. This is a collection of small objects that are still under the Sun’s gravitational influence. While the actual width of the Oort Cloud in not known, it is estimated to extend from roughly 1000 AU to about 100,000 AU (an astronomical unit, or AU, is the distance from the Earth to the Sun and is the standard measurement used when calculating distances within our solar system).
Given this estimation, it will likely be another 300 years before Voyager 2 reaches the inner edge of the Oort Cloud at its current speed. That means it could take 30,000 years to fly beyond it.
“I think we’re all happy and relieved that the Voyager probes have both operated long enough to make it past this milestone,” said Suzanne Dodd, Voyager project manager at NASA’s JPL. “This is what we’ve all been waiting for. Now, we’re looking forward to what we’ll be able to learn from having both probes outside the heliopause.”