Voyager 1 completed its primary mission in 1989, and then kept on flying toward the edge of the heliosphere, the huge bubble of charged particles and magnetic fields that the sun puffs out around itself. Voyager 1 has now popped free of this bubble into the exotic and unexplored realm of interstellar space, the scientists behind the latest study said.
They reached this historic conclusion with a little help from the sun. A powerful solar eruption caused electrons in Voyager 1's location to vibrate significantly between April 9 and May 22 of this year. The probe's plasma wave instrument detected these oscillations, and researchers used the measurements to figure out that Voyager 1's surroundings contained about 0.005 electrons per cubic inch (0.08 electrons per cubic centimeter).
That's far higher than the density observed in the outer regions of the heliosphere (roughly 0.0001 electrons per cubic inch, or 0.002 electrons per cubic cm) and very much in line with the 0.006 electrons per cubic inch (0.10 electrons per cubic cm) or so expected in interstellar space. [Photos from NASA's Voyager 1 and 2 Probes]
"We literally jumped out of our seats when we saw these oscillations in our data — they showed us that the spacecraft was in an entirely new region, comparable to what was expected in interstellar space, and totally different than in the solar bubble," study lead author Don Gurnett of the University of Iowa, the principal investigator of Voyager 1's plasma wave instrument, said in a statement.
It may seem surprising that electron density is higher beyond the solar system than in its extreme outer reaches. Interstellar space is, indeed, emptier than the regions in Earth's neighborhood, but the density inside the solar bubble drops off dramatically at great distances from the sun, researchers said.
CREDIT FOR CONTENT: Mike Wall Space.com
Image Credit: NASA
An artist's illustration of NASA's Voyager 1 spacecraft, the farthest human-built object from Earth, which launched in 1977 and has left our solar system