On August 25, sensors on the probe detected a sharp decline in the low-energy particles from solar wind, and a corresponding permanent increase in high-energy cosmic rays. Since these particles from our sun were expected to stay within the heliosphere, and cosmic rays from outside this safety-bubble supposedly could not penetrate it, scientists were nearly ready to declare mankind had finally officially left the solar system.
After a third test however, sensor readings revealed this threshold was not as simple as suspected.
If Voyager 1 had truly completely left the heliosphere, this third test would reveal a change in magnetic field orientation, which it did not. ”If we had only looked at particle data alone, we would have said we’re out. Goodbye, solar system,” said Stamatios Krimigis, of the Johns Hopkins University Applied Physics Laboratory, lead investigator of the low-energy charged particle instrument aboard Voyager 1. “Nature is imaginative.”
Because of this, Leonard Burlaga, a member of the team that operates Voyager’s magnetometer from NASA’s Goddard Space Flight Center in Greenbelt, Md. said, “there’s no evidence we’ve entered interstellar space.”
Instead, Krimigis and former Jet Propulsion Laboratory Director Edward Stone announced to the annual meeting of the American Geophysical Union in San Francisco what they described as a “magnetic highway.”
Created by a magnetic field originating from the southern hemisphere of the sun, this newly-discovered region connects the heliosphere to interstellar space and allows particles from either side to pass freely in and out along the field.
In December 2004, Voyager 1 passed the termination shock, entering a region called the heliosheath, where the solar wind slows drastically from a million miles-per-hour and becomes turbulent. The environment around Voyager 1 remained consistent from December 2004 until the summer of 2012.
There are now multiple theoretical models of the magnetic highway, but since NASA hadn’t even predicted it would exist, researchers can only speculate on the time it will take for Voyager 1 to cross this new region. ”It could take several more months or take several more years, but we believe this may be the very last layer between us and interstellar space,” Stone said.
Researchers are confident Voyager 1 will pass completely into interstellar space before then, along with it’s twin, Voyager 2, following about 2 billion miles behind.