For months, space enthusiasts have been sitting on the edges of their seats, ready for the Voyager 1 spacecraft to become the first emissary of human civilization to cross from the bubble around our sun* into interstellar space. Last August, two of the three instruments on Voyager 1 started sending back signals that something was -- suddenly, dramatically -- different. Particles from our sun fell way off, and cosmic rays from outside our system shot up. Was this the moment we'd all been waiting for?
Well, not quite yet. That third indicator -- the magnetic field data -- has turned out to be a bit, well, stubborn, showing month after month that Voyager is still in our sun's magnetic field. Two out of three ain't bad, as they say, but scientists need all three boxes checked before they will officially say that Voyager has crossed over, NASA explained in a release today.
Now scientists are giving Voyager's current home a new name -- the heliosheath depletion region. As Kelly Oakes writes in a terrific explanation in Scientific American:
Yep, what Voyager's instruments are now showing us is so odd we need a new name for it. Voyager is, almost literally, pushing the boundaries of our knowledge about the solar system.
Which, if you think about it, is hardly surprising. As Stamatios Krimigis of John Hopkins University, Maryland, and his colleagues write in one of the three papers out today, our ideas about the size and shape of the bubble of plasma we call the heliosphere, created by the solar wind that continuously flows from the sun, are older than the space age.
A trio of papers published in Science today details what scientists know about this new region, including two temporary shifts in the magnetic field data that occurred on May 29 and September 26 of last year, both times reverting to the data associated with our heliosphere (the bubble of solar winds emanating from our sun).
Voyager 1 launched in 1977 and has been traveling at astounding speeds for nearly 36 years (around 38,000 miles per hour currently). It is now more than 11 billion miles away from the sun. As we wait for it to reach its next and perhaps final frontier, scientists don't have a clear idea of what to expect. "I mean this is the first time any spacecraft has been there," Voyager project scientist Ed Stone of Caltech said to me last year.
We didn't know that the "heliosheath depletion region" was going to be there, or that it was going to be this big, but now that Voyager's been there for a while, we may as well give it a name. And while Voyager's departure from our heliosphere might not be the sort of clean, sudden that many of us would find satisfying, the new region is, well, a new region -- a piece of our little home in the universe that we didn't know about before, and now, thanks to Voyager, we do.
*Clarification and correction: Technically, Voyager 1 is on the boundary between interstellar space and the heliosphere, not the solar system, because the solar system extends far beyond the heliosphere (the bubble of the solar winds) to include all objects influenced by the sun's gravity, which includes the Oort cloud, approximately a light year away -- much, much farther than Voyager 1 is now. An earlier version said "solar system" in spots where I was technically referring to the heliosphere. Thanks to Tom Standage for bringing this up on Twitter.