It's natural to want a change of pace after 41 years of the same old scene.
Voyager 2 has become the second man-made object to cross out of the heliosphere — the bubble of particles and magnetic fields generated by the sun — and cross into interstellar space. Its companion spacecraft, Voyager 1, crossed into the same realm in 2012.
"We've been waiting with bated breath for the last couple of months for us to be able to see this," Nicola Fox, director of NASA's heliophysics division, said during a Dec. 10 news conference at a meeting of the American Geophysical Union in Washington, D.C.
There goes the heliosphere
Voyager 2 likely zipped through the heliosphere sometime around Nov. 5, which is when NASA noticed that the craft's Plasma Science Experiment (PLS) reported a steep decline in the speed of solar wind particles emitted by our sun. Other instruments, including the cosmic ray subsystem, the low-energy charged particle instrument and the magnetometer, noticed an uptick in galactic cosmic rays. Put these findings together and scientists feel confident that Voyager 2 has sailed into this other region of space.
"Working on Voyager makes me feel like an explorer, because everything we're seeing is new," John Richardson, principal investigator for the PLS instrument and a principal research scientist at the Massachusetts Institute of Technology, said in a NASA statement. "Even though Voyager 1 crossed the heliopause in 2012, it did so at a different place and a different time, and without the PLS data. So we're still seeing things that no one has seen before."
This illustration shows the position of Voyager 1 and Voyager 2 probes, outside of the heliosphere. Voyager 1 exited the heliosphere in August 2012. Voyager 2 exited at a different location on November 2018. (Photo: NASA/JPL-Caltech)
Voyager 2 may be around 11 billion miles (18 billion kilometers) from Earth, but NASA can still communicate with it. Both NASA and Voyager 2 can beam back data and instructions at the speed of light, but it'll take around 16.5 hours for the transmission to reach its destination. For comparison's sake, it takes about eight minutes for the light of the sun to reach Earth.
Together, the Voyagers are expected to provide a better understanding of how the heliosphere interacts with the ever-flowing interstellar wind beyond it.
"There is still a lot to learn about the region of interstellar space immediately beyond the heliopause," said Ed Stone, Voyager project scientist based at Caltech in Pasadena, California.
Both Voyager spacecraft won't be getting out of our solar system any time soon, however. That boundary is considered to the be the edge of the Oort Cloud, a collection of celestial objects on which the sun's gravity still has some influence. We're not sure how far the Oort Cloud extends, but scientists estimate that it begins at 1,000 astronomical units (AUs) from the sun and extends out for about 10,000 AU. A single AU is the distance from the sun to the Earth. Voyager 2 would need about 300 years to reach it and another 30,000 years, at least, to pass through it.
Records of human history
Should Voyager 2 ever get that far, it would be quite the feat.
Launched in 1977 and only 16 days apart, Voyagers 1 and 2 were both built to only last for five years to conduct close-up surveys of Jupiter and Saturn. However, opportunities arose to explore Neptune and Uranus as well. Relying on remote-controlled reprogramming, scientists were able to give the crafts upgrades that exceeded their original software, thus extending the value of the crafts' mission. At 41 years old, Voyager 2 is NASA's longest-running mission.
The Voyager crafts may be best known to the public for their cargo, however. Both carry with them Golden Records of Earth. These capsules contain 115 images and a variety of natural sounds — like thunder, animals and surf — selected by a committee headed up by Carl Sagan. Musical selections from different cultures and periods were also included, spoken greetings in 55 different languages and printed messages from then-President Jimmy Carter and then-U.N. Secretary-General Kurt Waldheim. Symbolic instructions explain the origins of each craft and how to play the records using the included needle.
As both Voyagers could potentially last for billions of years, they could very well end up being the only traces of human existence in the universe after we're gone.