Voyager 2 spacecraft sends first messages from interstellar space
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Twelve billion miles from Earth, there is an elusive boundary that marks the edge of the sun’s realm and the start of interstellar space. When Voyager 2, the longest-running space mission, crossed that frontier more than 40 years after its launch it sent a faint signal from the other side that scientists have now decoded.
The Nasa craft is the second ever to travel beyond the heliosphere, the bubble of supersonic charged particles streaming outwards from the sun. Despite setting off a month ahead of its twin, Voyager 1, it crossed the threshold into interstellar space more than six years behind, after taking the scenic route across the solar system and providing what remain the only close-up images of Uranus and Neptune.
Now Voyager 2 has sent back the most detailed look yet at the edge of our solar system – despite Nasa scientists having no idea at the outset that it would survive to see this landmark.
The U.S. space agency previously announced that Voyager 2, the second human-made object ever to depart the solar system following its twin Voyager 1, had zipped into interstellar space on Nov. 5, 2018 at a point more than 11 billion miles (17.7 billion km) from the sun. Several research papers published on Monday provided scientific details of that crossing.
Both Voyager 1 and Voyager 2 were launched in 1977, designed for five-year missions. Voyager 1 left the solar system at a different location in 2012. Both are now traversing the Milky Way galaxy’s interstellar medium, a chillier region filling the vast expanses between the galaxy’s stars and planetary systems.
“This is a very exciting time for us,” California Institute of Technology physicist Edward Stone, project manager of the Voyager program, told reporters. “We will see a transition from the magnetic field inside to a different magnetic field outside, and we continue to have surprises compared to what we had expected.”
The electromagnetic junction just outside the heliosphere was thought to be a deeper transitional place of intermingling cosmic weather, but Voyager 2’s plasma wave instrument – built by University of Iowa researchers – detected sharp jumps in plasma density, much like two different fluids coming into contact with one another.
Scientists are still trying to understand the nature of interstellar space wind and how much of it can seep through the heliopause to reach planets in our solar system.
“We also have galactic cosmic rays, which are out in the interstellar space trying to flow in,” Stone said, referring to the high-energy atomic particles whizzing around the universe faster than the speed of light. “And some of them, only about 30 percent of what’s outside, can actually reach Earth.”
The research was published in the journal Nature Astronomy.
