Voyager may not be in interstellar space

In 2012, Voyager 1 crossed into interstellar space, but it might not have reached this historic milestone at all. Despite observations suggesting the spacecraft has crossed the boundary, there is uncertainty as to whether it has truly crossed into interstellar space or if it is still in the heliosphere. Two Voyager team scientists have developed a new test which they say could prove once and for all where the spacecraft is. The model assumes the solar wind is slowing down and as a result can be compressed; if so, Voyager 1 should be moving faster than the outward flow of solar wind and will encounter sheets where the polarity of the sun’s magnetic field will reverse. Voyager 1 should cross the current sheet and the polarity change from plus to minus within the next two years, the duo say. Voyager should detect this reversal, proving it has crossed the boundary – if that doesn’t happen then this is confirmation that the spacecraft is already in interstellar space. “If that happens, I think if anyone still believes Voyager 1 is in the interstellar medium, they will really have something to explain,” said George Gloeckler, professor in atmospheric, oceanic and space science at the University of Michigan in Ann Arbor. “The proof is in the pudding. This controversy will continue until it is resolved by measurements.” Gloeckler, lead author of the study in Geophysical Research Letters, has worked on the Voyager mission since 1972 and has been a vocal opponent that Voyager 1 has crossed into interstellar space. He said that although many signs indicating it might have crossed the divide - like cosmic rays - have been observed, the magnetic field switch has not. If the prediction is right, “this will be the highlight of my life,” he said. “There is nothing more gratifying than when you have a vision or idea and you make a prediction and it comes true.” Alan Cummings, co-investigator on the Voyager mission believes Voyager 1 has most likely crossed into interstellar space but there is a possibility that Gloeckler and colleague Len Fisk are correct. If the spacecraft experiences a current sheet crossing like the one proposed, it could also mean the heliosphere is expanding and crossed the spacecraft again, he said. “If the magnetic field had cooperated, I don’t think we’d be having this discussion,” he added. “This is a puzzle. It is very reasonable to explore alternative explanations. We don’t understand everything that happened out there.” A test for whether or not Voyager 1 has crossed the heliopause