Steve Cole
Headquarters, Washington
202-358-0918
stephen.e.cole@nasa.gov
Jia-Rui C. Cook/Alan Buis
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-0850/818-653-8339
jccook@jpl.nasa.gov/alan.buis@jpl.nasa.gov
RELEASE: 11-402
NASA'S VOYAGER HITS NEW REGION AT SOLAR SYSTEM EDGE
WASHINGTON -- NASA's Voyager 1 spacecraft has entered a new region
between our solar system and interstellar space. Data obtained from
Voyager over the last year reveal this new region to be a kind of
cosmic purgatory. In it, the wind of charged particles streaming out
from our sun has calmed, our solar system's magnetic field piles up
and higher energy particles from inside our solar system appear to be
leaking out into interstellar space.
"Voyager tells us now that we're in a stagnation region in the
outermost layer of the bubble around our solar system," said Ed
Stone, Voyager project scientist at the California Institute of
Technology in Pasadena. "Voyager is showing that what is outside is
pushing back. We shouldn't have long to wait to find out what the
space between stars is really like."
Although Voyager 1 is about 11 billion miles (18 billion kilometers)
from the sun, it is not yet in interstellar space. In the latest
data, the direction of the magnetic field lines has not changed,
indicating Voyager is still within the heliosphere, the bubble of
charged particles the sun blows around itself. The data do not reveal
exactly when Voyager 1 will make it past the edge of the solar
atmosphere into interstellar space, but suggest it will be in a few
months to a few years.
The latest findings, described today at the American Geophysical
Union's fall meeting in San Francisco, come from Voyager's Low Energy
Charged Particle instrument, Cosmic Ray Subsystem and Magnetometer.
Scientists previously reported the outward speed of the solar wind had
diminished to zero in April 2010, marking the start of the new
region. Mission managers rolled the spacecraft several times this
spring and summer to help scientists discern whether the solar wind
was blowing strongly in another direction. It was not. Voyager 1 is
plying the celestial seas in a region similar to Earth's doldrums,
where there is very little wind.
During this past year, Voyager's magnetometer also detected a doubling
in the intensity of the magnetic field in the stagnation region. Like
cars piling up at a clogged freeway off-ramp, the increased intensity
of the magnetic field shows that inward pressure from interstellar
space is compacting it.
Voyager has been measuring energetic particles that originate from
inside and outside our solar system. Until mid-2010, the intensity of
particles originating from inside our solar system had been holding
steady. But during the past year, the intensity of these energetic
particles has been declining, as though they are leaking out into
interstellar space. The particles are now half as abundant as they
were during the previous five years.
At the same time, Voyager has detected a 100-fold increase in the
intensity of high-energy electrons from elsewhere in the galaxy
diffusing into our solar system from outside, which is another
indication of the approaching boundary.
"We've been using the flow of energetic charged particles at Voyager 1
as a kind of wind sock to estimate the solar wind velocity," said Rob
Decker, a Voyager Low-Energy Charged Particle Instrument
co-investigator at the Johns Hopkins University Applied Physics
Laboratory in Laurel, Md. "We've found that the wind speeds are low
in this region and gust erratically. For the first time, the wind
even blows back at us. We are evidently traveling in completely new
territory. Scientists had suggested previously that there might be a
stagnation layer, but we weren't sure it existed until now."
Launched in 1977, Voyager 1 and 2 are in good health. Voyager 2 is 9
billion miles (15 billion kilometers) away from the sun.
The Voyager spacecraft were built by NASA's Jet Propulsion Laboratory
in Pasadena, Calif., which continues to operate both. JPL is a
division of the California Institute of Technology. The Voyager
missions are a part of the NASA Heliophysics System Observatory,
sponsored by the Heliophysics Division of the Science Mission
Directorate in Washington. For more information about the Voyager
spacecraft, visit:
http://www.nasa.gov/voyager For more information about NASA media events at the American
Geophysical Union meeting, visit:
http://www.nasa.gov/agu
