It
appears we have now finally left the leading edge of the heliosphere.
There may be some other unimagined effect to discover, but that
appears rather unlikely really. I think we are cleanly out of it.
The
switch from one regime to another was clear and quick as one would
reasonably expect.
In
reality, we have had little in the way of real surprises here. There
was a bow wave and we passed through it. It was a lot thicker than
expected perhaps, but that was unfounded opinion anyway.
In
the meantime, media coverage remains slight and it should be
otherwise. The solar envelope is very real and will be our abode
once we master magnetic field exclusion propulsion methods able to
let us operate at an acceleration of one g.
Voyager 1 enters
new region of space
Thirty-five years
after its launch, Voyager 1 appears to have travelled beyond the
influence of the Sun and exited the heliosphere, according to a new
study appearing online today.
The heliosphere is a
region of space dominated by the Sun and its wind of energetic
particles, and which is thought to be enclosed, bubble-like, in the
surrounding interstellar medium of gas and dust that pervades the
Milky Way galaxy.
On August 25, 2012, NASA's Voyager 1 spacecraft measured drastic changes in radiation levels, more than 11 billion miles from the Sun. Anomalous cosmic rays, which are cosmic rays trapped in the outer heliosphere, all but vanished, dropping to less than 1 percent of previous amounts. At the same time, galactic cosmic rays -- cosmic radiation from outside of the solar system -- spiked to levels not seen since Voyager's launch, with intensities as much as twice previous levels.
The findings have been accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union.
"Within just a few days, the heliospheric intensity of trapped radiation decreased, and the cosmic ray intensity went up as you would expect if it exited the heliosphere," said Bill Webber, professor emeritus of astronomy at New Mexico State University in Las Cruces. He calls this transition boundary the "heliocliff."
In the GRL article, the authors state: "It appears that [Voyager 1] has exited the main solar modulation region, revealing [hydrogen] and [helium] spectra characteristic of those to be expected in the local interstellar medium."
However, Webber notes, scientists are continuing to debate whether Voyager 1 has reached interstellar space or entered a separate, undefined region beyond the solar system.
"It's outside the normal heliosphere, I would say that," Webber said. "We're in a new region. And everything we're measuring is different and exciting."
The work was funded by NASA's Jet Propulsion Laboratory in Pasadena, Calif.
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