Scientists are arguing about whether Voyager has left the Solar System

NASA

Has Voyager 1 reached interstellar space or not? That question was first asked about a year ago, when the probe first started seeing a drop-off in the levels of energetic particles emitted by the Sun, accompanied by a rise in cosmic rays from interstellar space. But the models of the Solar System's edge had suggested that there should be a corresponding change in the magnetic field's orientation as the Sun's field is overwhelmed by that of the galaxy as a whole. And Voyager 1 is seeing nothing of the sort; even as particle levels flip-flopped several times, the magnetic field remained largely stable.

There have been a couple interpretations of this. The scientists who first announced the results argued that the data showed evidence that a new, previously unpredicted region exists at the edge of the Solar System and that we would have to wait before we would be able to sample the interstellar magnetic field. But later that year, a different team argued that the probe was in interstellar space. It's just that interstellar space wasn't looking like we expected.

Now, a new paper has come out that revisits the cause of the problems: the models of the magnetic fields that exist where there's a complex interaction between two magnetic fields and two different flows of charged particles colliding. Earlier models of this region had been the ones that suggested the orientation of the magnetic field would change as the interstellar field wrapped gently around the one generated by our Sun. The new one, however, suggests that the interstellar field lines run directly up against the ones from our Sun, at which point they execute a nearly right-angled turn, leaving the two sets to travel parallel.