Be thankful that there are no small children on board NASA’s Voyager 1 – the cries of “Are we nearly there yet?” would be unbearable. It has flown further from Earth than any other spacecraft, but still has not left the solar system, despite multiple claims over the past decade that it was on the brink of doing so.
Part of the problem is that we do not know exactly where the boundary of the solar system is – only that it is marked by the edge of a magnetic bubble known as the heliopause, at which the influence of other stars starts to dominate that of the sun.
Voyager 1 has been drifting through the outer layer of this boundary, the heliosheath, since 2005. Readings reported today suggest that although the craft has experienced yet more changes to its surroundings, it has yet to say, “Sayonara, solar system.”
Instead Voyager 1 seems to be skirting on the edge of yet another phase of the heliosheath, dubbed the heliosheath depletion region. The craft crossed in and out of this region five times last year – an indication that the boundary is rippled and turbulent. Each time the strength of the heliosheath’s magnetic field spiked while the number of charged particles fell. Instruments also recorded a rise in interstellar cosmic rays.
The direction of the magnetic field did not change however, suggesting the craft has not yet escaped the sun’s clutches. Better luck next time, V1.
For full details on Voyager 1’s adventures at the cusp of interstellar space, read our story from last September, “Voyager 1: reports of my exit are greatly exaggerated”.
Journal references: Science, DOIs: 10.1126/science.1235451 and10.1126/science.1235721