The Voyager 1 spacecraft was in the news a few months ago when it was falsely reported that it had left the solar system. It still hasn’t left the Sun’s magnetic field, but NASA says it is at the final barrier of the heliosphere. It could still be months or years before Voyager 1 crosses that barrier, but when it does it will be the first human-made craft to enter interstellar space.
There are already signs that Voyager 1 is approaching interstellar space. NASA scientists have seen charged particles that disappear as they move out along the edge of the Sun’s magnetic field. They’ve also seen cosmic rays from outside the solar system coming in. These are both signs that Voyager 1 is on the edge of interstellar space.
What they haven’t seen is the expected change in the direction of the magnetic field, and that’s the last marker they’re looking for before being able to declare that Voyager is in interstellar space and out of our solar system.
Voyager project scientist Ed Stone from the California Institute of Technology said:
This strange, last region before interstellar space is coming into focus, thanks to Voyager 1, humankind’s most distant scout. 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.
Part of the problem with estimating when Voyager will leave the heliosphere and enter interstellar space is that we don’t really know how far the heliosphere extends. Finding that out is part of the Voyager mission. As Voyager 1 reaches the very edge of our solar system, scientists will continue to monitor the magnetic field for signs of interstellar space.
It’s not certain when Voyager 1 will cross that final threshold, but the NASA scientists monitoring the craft will know it when they see it.
(via NASA, image via NASA/JPL-Caltech)
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