Voyager 2 has left behind the solar winds encompassing our sun and will now give us a glimpse into "truly uncharted territory." The NASA space probe is the second human-made object in history to pass this milestone.
Image: picture alliance/JPL-Caltech/NASA/dpa
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Over 40 years after it left planet Earth, the Voyager 2 space probe has crossed over into interstellar space, NASA announced on Monday.
The US space agency said that the spacecraft has exited the outer boundary of the heliosphere — the bubble of solar wind that the sun creates around itself — in early November.
Voyager 2 is now some 11 billion miles (about 18 billion kilometers) from Earth and is the second human-made object to pass into the vast area of interstellar space.
NASA was able to determine Voyager 2's position based on data gathered from one of its key instruments — a Plasma Science Experiment (PLS). The instrument recorded a steep drop in the speed of solar wind particles on November 5 and hasn't recorded any solar wind flow since.
Both the Voyager 1 and Voyager 2 launched from the US in 1977Image: picture alliance/Jet Propulsion Lab via AP/dpa
'Unprecedented glimpse' into interstellar space
Nicola Fox, director of the Heliophysics Division at NASA Headquarters, said in a statement that the Voyager probes have a "special place" in her department.
"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," she added.
Both the Voyager 1 and Voyager 2 launched from the US in 1977 and have carried out flyby missions on Jupiter, Saturn, Uranus and Neptune — extending long past their five-year lifespans.
Mission operators are still able to communicate with Voyager 2, although it currently takes 16.5 hours for information to travel from the probe back to Earth since the data is moving at the speed of light.
"By comparison, light traveling from the Sun takes about eight minutes to reach Earth," NASA said in its statement.
Voyager: Two NASA spacecraft on tour
On August 20, 1977, spacecraft Voyager 2 took off to explore our galaxy. Voyager 1 followed 16 days later. Now there's news from interstellar space.
Image: picture-alliance/dpa/NASA JPL
Two sister probes
On August 20th, 1977 NASA launched Voyager 2 for a record flight that is still going. Shortly after, on September 5th, the identically built Voyager 1 followed. The initial aim of the mission was to obtain more information about Jupiter and Saturn — planets which were still largely unexplored at the time. Thanks to the long-lasting plutonium batteries, both spacecrafts are still active.
Image: REUTERS/NASA/JPL-Caltech
Staying power
Weighing 825kg (1,818 pounds) on Earth, the Voyager probes are among NASA's biggest success stories. Both still regularly send reliable data from space. They're moving farther and farther away from Earth, but the radio connection is expected to work until 2030.
Image: public domain
Leaving the solar system
On August 25th, 2012 Voyager 1 crossed the heliopause — one of the borders of our solar system. There, the interstellar space of our galaxy, the Milky Way, begins. Voyager 1 is the furtherst human-made object from Earth.
Image: picture-alliance/dpa
Diving into interstellar space
A short time later Voyager 2 followed. On November 5, 2018, the sister probe dived into interstellar space. The evaluation of the measurements has now yielded surprising results and thrown some historical theories overboard.
Image: picture alliance/Jet Propulsion Lab via AP/dpa
At the edge of the space bubble
The solar system has different borders: The first is the "termination shock." That's where the solar winds slow down dramatically. After the heliosphere comes the heliopause. That's the edge of the space bubble where solar flares shield us from interstellar rays. Until now, the assumption was that the winds gradually decreased.
Image: picture-alliance/dpa/NASA JPL
Here it gets exciting!
But the comparative measurements of the two sister probes have shown that there is a very sharp boundary in the interior of our solar system. And the temperature of the interstellar medium is significantly higher than expected. The researchers suspect that the heliosphere could push a kind of bow wave through the interstellar medium in front of it, but this has yet to be measured.
Image: picture alliance/dpa/Nasa
Jupiter from all angles
Aside from the interstellar discoveries, the spacecrafts had much more to absorb. Voyager 1 sent this image of Jupiter on January 1, 1979. It took a total of 17,477 images of the planet and its four moons in total. The existence of the thin ring system surrounding Jupiter was detected for the first time through these images.
Image: picture-alliance/dpa/NASA
Swirling masses up close
Voyager 1 also documented atmospheric flows on Jupiter, as seen in this picture. After the Jupiter flyby, Voyager 1 reached a speed of 16 kilometers per second.
Image: picture-alliance/dpa/NASA
Saturn's beige, apparently
Voyager 2 sent this full-color photo of Saturn back to Earth. The probe reached the sixth planet in our solar system in 1981. In outer space terms, this photo is a real close-up — it was taken from a distance of just 21 million kilometers (about 13 million miles).
Image: HO/AFP/Getty Images
Everything's under control
The distant probes are monitored and controlled as closely as they can be by the control center of the Voyager mission at the California Institute of Technology in Pasadena, seen here in 1980. Today, the equipment is much more modern. But NASA regularly has to consult with the engineers who designed and built the Voyager spacecraft — even though they are long retired.
Image: NASA/Hulton Archive/Getty Images
Sounds of Earth for alien ears
In the event the probes encounter life on their endless journey, they have these shiny gold discs along for the ride. The records contain pictures and sounds of people, animals and nature on Earth. In case the aliens don't own a record player, a needle and detailed instructions are provided.
Image: NASA/Hulton Archive/Getty Images
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Not leaving solar system soon
NASA estimates that the probes could last another five to 10 years, but the extreme cold outside the vehicles and their waning power supply means they will eventually become less useful, said Voyager project manager Suzanne Dodd.
"I think we're all happy and relieved that the Voyager probes have both operated long enough to make it past this milestone," Dodd said.
Both of the spacecraft are still technically in our solar system, as they have yet to pass beyond it's outer edge known as the Oort Cloud.
It could be another 30,000 years before they would fly beyond it and come close to other stars, NASA said.
In the meantime, the probes are still sending crucial information back to Earth about the area beyond the heliosphere — and the space between the stars.
