MessageToEagle.com - Data from NASA's Voyager 1 spacecraft indicate that our deep-space explorer
is now more than 11 billion miles (18 billion kilometers) from the sun, reaching interstellar space.
Scientists have seen two of the three signs of interstellar arrival they expected to see: charged particles
disappearing as they zoom out along the solar magnetic field, and cosmic rays from far outside zooming in.
Scientists have not yet seen the third sign, an abrupt change in the direction of the magnetic field, which
would indicate the presence of the interstellar magnetic field.
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This artist's concept shows NASA's two Voyager spacecraft exploring a turbulent region of space known as the
heliosheath, the outer shell of the bubble of charged particles around our sun. Image Credit: NASA/JPL-Caltech
"This strange, last region before interstellar space is coming into focus, thanks to Voyager 1, humankind's
most distant scout," said Ed Stone, Voyager project scientist at the California Institute of Technology
"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."
The heliosphere extends at least 8 billion miles (13 billion kilometers) beyond all the planets in our
solar system. It is dominated by the sun's magnetic field and an ionized wind expanding outward from the sun.
Outside the heliosphere, interstellar space is filled with matter from other stars and the magnetic field
present in the nearby region of the Milky Way.
"We saw a dramatic and rapid disappearance of the solar-originating particles. They decreased in intensity
by more than 1,000 times, as if there was a huge vacuum pump at the entrance ramp onto the magnetic highway,"
said Stamatios Krimigis, the low-energy charged particle instrument's principal investigator at the Johns
Hopkins University Applied Physics Laboratory in Laurel, Md.
This artist's concept shows NASA's Voyager 1 spacecraft exploring a region called the "depletion region" or "magnetic highway" at the outer limits of our
heliosphere, the bubble the sun blows around itself. Image credit: NASA/JPL-Caltech
"We have never witnessed such a decrease before, except when Voyager 1 exited the giant magnetosphere of
Jupiter, some 34 years ago."
Other charged particle behavior observed by Voyager 1 also indicates the spacecraft still is in a
region of transition to the interstellar medium and it's hard to say exactly how far Voyager 1 has to
go to reach interstellar space.
They estimate it could take several more months, or even years, to get there.