New research published in the journal Science indicates that Voyager 1 spacecraft has ente 
red the last frontier of the solar system and is poised to become the first man-made object to reach interstellar space. The spacecraft, which left Earth 35 years ago, is now than 11 billion miles from home at the edge of the heliosphere, a bubble of charged particles that the sun blows around itself.
“This strange, last region before interstellar space is coming into focus, thanks to Voyager 1, humankind’s most distant scout,” said Ed Stone, Voyager project scientist at the California Institute of Technology in Pasadena.
The authors say that they have observed two of the three signs that indicate that interstellar space is near. They’ve seen charged particles from the sun disappear and cosmic rays arriving from space intensify. But scientists have yet to detect the third sign, an abrupt change in the direction of the sun’s magnetic field, which would indicate the presence of the interstellar magnetic field.
“If you looked at the cosmic ray and energetic particle data in isolation, you might think Voyager had reached interstellar space, but the team feels Voyager 1 has not yet gotten there because we are still within the domain of the sun’s magnetic field,” Stone said.
When Voyager 1 and 2 launched in 1977, they were expected to last only a few years. “NASA considered everything past the Saturn encounter a bonus,” said Dr. Howard Butler, who ran GE’s Aerospace Electronic Systems Department. GE engineers designed the Voyagers’ command computers directing the flight path and providing communication links with NASA Mission Control, as well as the probes’ power source called radioisotope thermoelectric generators (RTGs). These devices still remain in service and convert the heat produced from the natural radioactive decay of plutonium into electricity for the spacecraft’s instruments, computers, radio and other systems.
