It has been 36 years since Voyager 1 was dispatched in 1977 on a mission to send back images of Jupiter’s atmosphere and volcanic eruptions on one of its moons, Io. Then it was due to travel to Saturn to examine that planet’s system of rings and moons. However, after traveling more than 11 billion miles, where is Voyager now? It seems that no one knows for sure.
NASA scientists, including Edward Stone, the father of the program at the US space agency’s Jet Propulsion Laboratory in Pasadena, California, say Voyager 1 has yet to pass beyond the sun’s radiation.
However, a controversial study published last week in the Astrophysical Journal claims NASA scientists misinterpreted magnetic field data and the satellite actually passed beyond the boundary known as the heliosheath a year ago. Put another way, Voyager 1 has left the solar system.
According to Marc Swisdak, an astrophysics researcher at the University of Maryland and lead author of the study, Voyager 1 made that giant leap on July 27 last year, when it recorded a permanent drop in heliosphere-produced particles and an increase in galactic cosmic rays from outside the solar system.
“Our three lines of data are consistent with Voyager being outside the solar system,” Swisdak said a week ago. “There’s a class of particles generated within the solar system and we’re not seeing them any more. Then there’s the question of the magnetic field. You can get outside the solar system without seeing too much of a shift in the data.”
As Voyager clears the distortion, the magnetic data will begin to conform, he said.
“This is the first opportunity to take actual direct measurements of the particles and the magnetic fields,” Swisdak said. “Instead of a indirect, complicated chains of arguments, we can say what’s actually out there — and that’s something rare in astronomy. Voyager is allowing us to see what’s really out there.”
NASA has yet to confirm the finding. Scientists at the California Institute of Technology, led by Stone, believe the craft is traveling through a mysterious region at the edge of the heliosphere. They have said they will know Voyager has left the solar system when magnetic fields emanate from the long arms of the galaxy, not the sun.
However, after running 100,000 processor hours of computer simulations on a Berkeley supercomputer called Hopper, Swisdak’s team claim the agency is failing to account for “magnetic reconnection” — when opposing magnetic field lines come together, snap and form new connections. They hypothesize that the magnetic fields of the sun and of interstellar space join in “magnetic islands” that make the border uneven.
Their study echoes claims made earlier this year and dismissed by NASA in the journal of the American Geophysical Union that Voyager 1 had traveled outside the solar system. This time, the agency has taken a more measured approach.
“The Voyager 1 spacecraft is exploring a region no spacecraft has ever been to before,” Stone said. “We will continue to look for any further developments over the coming months and years as Voyager explores an uncharted frontier.”
Conceived of to take advantage of a rare alignment of Jupiter, Saturn, Uranus and Neptune that occurs once every 175 years, NASA’s original program was designed for a “Grand Tour” of the solar system by harnessing the gravity of one planet to swing to the next. The mission’s two probes, Voyagers 1 and 2, used satellites designed to last just five years.
Yet they sail on at 55,000kph, using only essential instruments to ration power from plutonium batteries that are expected to last until about 2020.
Stone told Scientific American that leaving the solar system will be “a milestone in human activity.”