NASA’s Voyager 2 probe has left the heliosphere, the protective bubble of particles and magnetic fields created by the Sun, and is on its way into interstellar space.
By leaving the solar system, it has become the second spacecraft in the history of mankind to leave our solar system.
The probe, which launched in 1977 to study the planets farthest from Earth, has finally crossed the outermost edge of what’s called the heliosphere — a protective bubble created by our sun that engulfs all planets— on Nov. 5.
Artist’s concept of Voyager 2 with 9 facts listed around it. Image Credit: NASA
According to reports, as you are reading this, Voyager 2 is more than 11 billion miles from Earth. To get an idea of that distance, the sun is only 91 to 94.5 million miles from Earth.
By entering interstellar space, Voyager 2 is now travelling together with its sister probe Voyager 1, which crossed into interstellar space in 2012. Both probes are now travelling in the space between stars.
But how do we know that Voyager 2 is really travelling in interstellar space?
As explained by NASA, the most compelling evidence of Voyager 2’s entrance into interstellar space came from its onboard Plasma Science Experiment (PLS). Curiously, this instrument stopped working on Voyager 1 in 1980, long before that probe crossed the heliopause, in 2012.
Until a month ago, the space surrounding Voyager 2 was filled predominantly with plasma originating from our Sun.
This outflow is what scientists call solar wind. The solar wind creates the bubble – the heliosphere – enveloping all cosmic objects within our solar system.
Voyager’s 2 PLS instrument makes use of the electrical current of the plasma that comes from the sun to detect speed, density, temperature, pressure, and flux of the solar wind.
The PLS aboard Voyager 2 reported a steep decline in the speed of the solar wind particles on Nov. 5.
Scientists have found that since that date, the plasma instrument has observed no solar wind flow in the space through which Voyager 2 is currently travelling, which makes mission scientists confident the spacecraft has successfully left the heliosphere.
“Working on Voyager makes me feel like an explorer because everything we’re seeing is new,” said John Richardson, principal investigator for the PLS instrument and a principal research scientist at the Massachusetts Institute of Technology in Cambridge.
“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.”
And because instruments onboard Voyager 2 are still functioning, mission scientists are eager to see what new data the spacecraft will send about the environment through which the spacecraft is travelling.
“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.”
Voyager’s mission controllers communicate with the probes using NASA’s Deep Space Network (DSN).