NASA’s Voyager 2 has become the second human-made spacecraft in history to reach interstellar space. The probe has now exited the heliosphere, that is, the protective bubble of particles and magnetic fields created by the sun.
NASA’s scientists have determined that Voyager 2 crossed the outer edge of the heliosphere on November 5. This outer edge is known as the heliopause.
The heliopause is where the tenuous, hot solar wind meets the cold, dense interstellar medium. NASA’s Voyager 1 crossed this boundary in 2012. Voyager 2 carries a working instrument that will provide first-of-its-kind observations of the nature of this gateway into interstellar space.
Voyager 2 is now 11 billion miles from Earth, from where it will collect ground-breaking data. Mission operators can communicate with Voyager 2, but information being transmitted from the probe takes more than 16 hours to reach Earth.
“Working on Voyager makes me feel like an explorer, because everything we’re seeing is new,” John Richardson, principal investigator for the PLS (Plasma Science Experiment) instrument and a principal research scientist at the Massachusetts Institute of Technology in Cambridge, said in a 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.”
Voyager project scientist, Ed Stone, said, “There is still a lot to learn about the region of interstellar space immediately beyond the heliopause.”
Together, both Voyagers 1 and 2 provided a detailed glimpse of how our heliosphere interacts with the constant interstellar wind flowing from beyond. Their observations complement data from NASA’s Interstellar Boundary Explorer (IBEX), a mission that is remotely sensing that boundary.
NASA said it was also working on an additional mission – the upcoming Interstellar Mapping and Acceleration Probe (IMAP). The IMAP has been estimated to launch in 2024, and will capitalise on the Voyagers’ observations.
What is Voyager 2?
The Voyager 2 was the first of two twin probes NASA launched in 1977 to explore the outer planets of our solar system. While Voyager 1 focused on Jupiter and Saturn, Voyager 2 took close-up pictures of those planets as well as Uranus and Neptune.
Voyager 2 reached Jupiter in 1979, two years after launching from Cape Canaveral. Since Voyager 1 had already gone through the system four months earlier, Voyager 2’s arrival allowed NASA to take valuable comparison shots of Jupiter and its moons.
Voyager 2 took pictures of several Jupiter’s satellites. Among its most spectacular findings were pictures from the icy moon Europa. Voyager 2 was able to capture detailed photos of Europa’s cracks from 128,000 miles (205,996 km) away. The photos revealed that there’s no change in elevation anywhere on the moon’s surface.
In addition, Voyager 2 provided the only close-up glimpses of Uranus and Neptune. After both the Voyagers revealed the potential presence of water on Saturn, NASA’s Cassini probe unearthed evidence of the liquid at one of Saturn’s moons named Titan.
What next for Voyager 2?
At a news conference held at the annual meeting of the American Geophysical Union on December 10, scientists and engineers said that though they’re excited about the mission entering interstellar space, both Voyager 2 and its twin probe have plenty of life left in them.
The continuous data received from them will help shed light on how particles flowing off the sun collide with the particles on the interstellar wind.
The key challenge for the remainder of spacecraft operations will be coping with the gradual loss of heat and power. Voyager 2 is currently operating in temperatures of just about 38.5°F (3.6°C). With each passing year, the spacecraft’s power production reduces by 4 watts.
During the press conference, Suzanne Dodd, project manager for the Voyager Interstellar Mission, estimated that both Voyagers can operate for at least five, perhaps ten more years.
Dodd said that she aims to coerce full 50 years of exploration out of the spacecrafts since their launch in 1977.
Although neither Voyager’s instruments will last forever, the two spacecraft themselves will continue their journey across the solar system.
In about 300 years, they will reach the inner edge of the Oort Cloud – which is the sphere of comets surrounding our solar system. Crossing that field could take somewhere around 30,000 years.
Once the Voyager probes leave our solar system entirely, they’ll settle into a long orbit around the heart of the Milky Way galaxy for potentially billions of years.
Elton Gomes is a staff writer at Qrius.