The finding is reported in a paper published in the Sept. 12 online issue of the journalScience.
“On April 9, the Voyager 1 Plasma Wave instrument, built at the UI in the mid-1970s, began detecting locally generated waves, called electron plasma oscillations, at a frequency that corresponds to an electron density about 40 times greater than the density inside the heliosphere—the region of the sun’s influence,” says Gurnett. “The increased electron density is very close to the value scientists expected to find in the interstellar medium.
“This is the first solid evidence that Voyager 1 has crossed the heliopause, the boundary between the heliosphere, and interstellar space,” says Gurnett, principal investigator for the plasma wave instrument.
For several months, the relative position of Voyager 1 has stirred something of a scientific debate because there remains some lingering evidence of the nearby heliosphere beyond the heliopause.
Read more at: Phys.org