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Robert Pearlman
NASA release
NASA's Voyager Hits New Region at Solar System Edge
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.
Robert Pearlman
NASA release
Data from NASA's Voyager 1 point to interstellar future
Data from NASA's Voyager 1 spacecraft indicate that the venerable deep-space explorer has encountered a region in space where the intensity of charged particles from beyond our solar system has markedly increased. Voyager scientists looking at this rapid rise draw closer to an inevitable but historic conclusion – that humanity's first emissary to interstellar space is on the edge of our solar system.
"The laws of physics say that someday Voyager will become the first human-made object to enter interstellar space, but we still do not know exactly when that someday will be," said Ed Stone, Voyager project scientist at the California Institute of Technology in Pasadena. "The latest data indicate that we are clearly in a new region where things are changing more quickly. It is very exciting. We are approaching the solar system's frontier."
The data making the 16-hour-38 minute, 11.1-billion-mile (17.8-billion-kilometer), journey from Voyager 1 to antennas of NASA's Deep Space Network on Earth detail the number of charged particles measured by the two High Energy telescopes aboard the 34-year-old spacecraft. These energetic particles were generated when stars in our cosmic neighborhood went supernova.
"From January 2009 to January 2012, there had been a gradual increase of about 25 percent in the amount of galactic cosmic rays Voyager was encountering," said Stone. "More recently, we have seen very rapid escalation in that part of the energy spectrum. Beginning on May 7, the cosmic ray hits have increased five percent in a week and nine percent in a month."
This marked increase is one of a triad of data sets which need to make significant swings of the needle to indicate a new era in space exploration. The second important measure from the spacecraft's two telescopes is the intensity of energetic particles generated inside the heliosphere, the bubble of charged particles the sun blows around itself. While there has been a slow decline in the measurements of these energetic particles, they have not dropped off precipitously, which could be expected when Voyager breaks through the solar boundary.
The final data set that Voyager scientists believe will reveal a major change is the measurement in the direction of the magnetic field lines surrounding the spacecraft. While Voyager is still within the heliosphere, these field lines run east-west. When it passes into interstellar space, the team expects Voyager will find that the magnetic field lines orient in a more north-south direction. Such analysis will take weeks, and the Voyager team is currently crunching the numbers of its latest data set.
"When the Voyagers launched in 1977, the space age was all of 20 years old," said Stone. "Many of us on the team dreamed of reaching interstellar space, but we really had no way of knowing how long a journey it would be -- or if these two vehicles that we invested so much time and energy in would operate long enough to reach it.”
Launched in 1977, Voyager 1 and 2 are in good health. Voyager 2 is more than 9.1 billion miles (14.7 billion kilometers) away from the sun. Both are operating as part of the Voyager Interstellar Mission, an extended mission to explore the solar system outside the neighborhood of the outer planets and beyond. NASA's Voyagers are the two most distant active representatives of humanity and its desire to explore.
Robert Pearlman
NASA release
Voyager at 35: Break on Through to the Other Side
Thirty-five years ago Monday (Aug. 20), NASA's Voyager 2 spacecraft, the first Voyager spacecraft to launch, departed on a journey that would make it the only spacecraft to visit Uranus and Neptune and the longest-operating NASA spacecraft ever. Voyager 2 and its twin, Voyager 1, that launched 16 days later on Sept. 5, 1977, are still going strong, hurtling away from our sun. Mission managers are eagerly anticipating the day when they break on through to the other side — the space between stars.
"Even 35 years on, our rugged Voyager spacecraft are poised to make new discoveries as we eagerly await the signs that we've entered interstellar space," said Ed Stone, Voyager project scientist at the California Institute of Technology in Pasadena. "Voyager results turned Jupiter and Saturn into full, tumultuous worlds, their moons from faint dots into distinctive places, and gave us our first glimpses of Uranus and Neptune up-close. We can't wait for Voyager to turn our models of the space beyond our sun into the first observations from interstellar space."
Voyager 2 became the longest-operating spacecraft on Aug. 13, 2012, surpassing Pioneer 6, which launched on Dec. 16, 1965, and sent its last signal back to NASA's Deep Space Network on Dec. 8, 2000. (It operated for 12,758 days.)
Scientists eagerly awaiting the entry of the two Voyagers into interstellar space have recently seen changes from Voyager 1 in two of the three observations that are expected to be different in interstellar space. The prevalence of high-energy particles streaming in from outside our solar system has jumped, and the prevalence of lower-energy particles originating from inside our solar system has briefly dipped, indicating an increasing pace of change in Voyager 1's environment. Voyager team scientists are now analyzing data on the direction of the magnetic field, which they believe will change upon entry into interstellar space.
Notable discoveries by Voyager 2 include the puzzling hexagonal jet stream in Saturn's north polar region, the tipped magnetic poles of Uranus and Neptune, and the geysers on Neptune's frozen moon Triton. Although launched second, Voyager 1 reached Jupiter and Saturn before Voyager 2, first seeing the volcanoes of Jupiter's moon Io, the kinky nature of Saturn's outermost main ring, and the deep, hazy atmosphere of Saturn's moon Titan. Voyager 1 also took the mission's last image: the famous solar system family portrait that showed our Earth as a pale blue dot.
Voyager 2 is about 9 billion miles (15 billion kilometers) away from the sun, heading in a southerly direction. Voyager 1 is about 11 billion miles (18 billion kilometers) away from the sun, heading in a northerly direction. For the last five years, both spacecraft have been exploring the outer layer of the heliosphere, the giant bubble of charged particles the sun blows around itself.
"We continue to listen to Voyager 1 and 2 nearly every day," said Suzanne Dodd, Voyager project manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "The two spacecraft are in great shape for having flown through Jupiter's dangerous radiation environment and having to endure the chill of being so far away from our sun."
Dodd and her team have been carefully managing the use of power from the continually diminishing energy sources on the two spacecraft. They estimate that the two spacecraft will have enough electrical power to continue collecting data and communicating it back to Earth through 2020, and possibly through 2025. While no one really knows how long it will take to get to interstellar space, Voyager scientists think we don't have long to wait. And, besides, the first 35 years have already been a grand ride.
Robert Pearlman
NASA release
NASA Voyager 1 Probe Encounters New Region in Deep Space
NASA's Voyager 1 spacecraft has entered a new region at the far reaches of our solar system that scientists feel is the final area the spacecraft has to cross before reaching interstellar space.
Scientists refer to this new region as a magnetic highway for charged particles because our sun's magnetic field lines are connected to interstellar magnetic field lines. This connection allows lower-energy charged particles that originate from inside our heliosphere, or the bubble of charged particles the sun blows around itself, to zoom out and allows higher-energy particles from outside to stream in. Before entering this region, the charged particles bounced around in all directions, as if trapped on local roads inside the heliosphere.
The Voyager team infers this region is still inside our solar bubble because the direction of the magnetic field lines has not changed. The direction is predicted to change when Voyager breaks through to interstellar space. The new results were described at the American Geophysical Union meeting in San Francisco on Monday.
"Although Voyager 1 still is inside the sun's environment, we now can taste what it's like on the outside because the particles are zipping in and out on this magnetic highway," said Edward Stone, Voyager project scientist based at the California Institute of Technology, Pasadena. "We believe this is the last leg of our journey to interstellar space. Our best guess is it's likely just a few months to a couple years away. The new region isn't what we expected, but we've come to expect the unexpected from Voyager."
Since December 2004 when Voyager 1 crossed a point in space called the termination shock, the spacecraft has been exploring the heliosphere's outer layer, called the heliosheath. In this region, the stream of charged particles from the sun known as the solar wind abruptly slowed down from supersonic speeds and became turbulent. Voyager 1's environment was consistent for about five and a half years. The spacecraft then detected that the outward speed of the solar wind slowed to zero.
The intensity of the magnetic field also began to increase at that time.
Voyager data from two onboard instruments that measure charged particles showed the spacecraft first entered this magnetic highway region on July 28, 2012. The region ebbed away and flowed toward Voyager 1 several times. The spacecraft entered the region again Aug. 25 and the environment has been stable since.
"If we were judging by the charged particle data alone, I would have thought we were outside the heliosphere," said Stamatios Krimigis, principal investigator of the low-energy charged particle instrument, based at the Johns Hopkins Applied Physics Laboratory, Laurel, Md. "But we need to look at what all the instruments are telling us and only time will tell whether our interpretations about this frontier are correct."
Spacecraft data revealed the magnetic field became stronger each time Voyager entered the highway region; however, the direction of the magnetic field lines did not change.
"We are in a magnetic region unlike any we've been in before -- about 10 times more intense than before the termination shock -- but the magnetic field data show no indication we're in interstellar space," said Leonard Burlaga, a Voyager magnetometer team member based at NASA's Goddard Space Flight Center in Greenbelt, Md. "The magnetic field data turned out to be the key to pinpointing when we crossed the termination shock. And we expect these data will tell us when we first reach interstellar space."
Voyager 1 and 2 were launched 16 days apart in 1977 and at least one of the spacecraft visited Jupiter, Saturn, Uranus and Neptune. Voyager 1 is the most distant human-made object, about 11 billion miles (18 billion kilometers) away from the sun. The signal from Voyager 1 takes approximately 17 hours to travel to Earth. Voyager 2, the longest continuously operated spacecraft, is about 9 billion miles (15 billion kilometers) away from our sun. While Voyager 2 has seen changes similar to those seen by Voyager 1, the changes are much more gradual. Scientists do not think Voyager 2 has reached the magnetic highway.
The Voyager spacecraft were built and continue to be operated by NASA's Jet Propulsion Laboratory, in Pasadena, Calif. The Voyager missions are a part of NASA's Heliophysics System Observatory, sponsored by the Heliophysics Division of the Science Mission Directorate in NASA Headquarters in Washington.
Robert Pearlman
NASA release
NASA Voyager Status Update on Voyager 1 Location
"The Voyager team is aware of reports today [March 20, 2013] that NASA's Voyager 1 has left the solar system," Edward Stone, Voyager project scientist at the California Institute of Technology, Pasadena, said. "It is the consensus of the Voyager science team that Voyager 1 has not yet left the solar system or reached interstellar space."
"In Dec. 2012, the Voyager science team reported that Voyager 1 is within a new region called 'the magnetic highway' where energetic particles changed dramatically. A change in the direction of the magnetic field is the last critical indicator of reaching interstellar space and that change of direction has not yet been observed."
See here for discussion of NASA's Voyager missions and their interstellar mission.
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