21Mar2013

Voyager 1 Encounters New Region in Deep Space.

Thirty-six years ago, the Voyager 1 space probe was launched on a first-ever mission to fly past the planets Jupiter and Saturn.

 NASA’s Voyager 1 spacecraft has entered a new region at the far reaches of our solar system 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 of these magnetic field lines 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.

NASA’s Voyager 1 spacecraft has encountered a new region in deep space that gets it one step closer to interstellar space.

 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.

Schematic of the Voyager spacecraft carrying 1970’s technology

“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. At least one of the spacecraft has 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.

The craft’s daily radio reports sent back evidence that the Sun’s magnetic field lines was connected to interstellar magnetic fields. Lower-energy charged particles were zooming out and higher-energy particles from outside were streaming in.

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. Caltech manages JPL for NASA. The Voyager missions are a part of NASA’s Heliophysics System Observatory, sponsored by the Heliophysics Division of the Science Mission Directorate at NASA Headquarters in Washington.

 

Voyager – A Short History


The golden record is mounted on its flight bracket on the mission module of the Voyager 1 spacecraft.

The spacecraft’s journey started in 1966 when Gary Flandro, then a graduate student working at NASA’s Jet Propulsion Laboratory, discovered that the planets were about to align. Not just for him, but for the whole solar system.He found that in the late 1970s and early 1980s, Jupiter, Saturn, Uranus, Neptune, and Pluto would be at the right relative positions in their orbits that a spacecraft could visit each of them on a grand tour. The secret was gravity assists, using the planets’ gravity to slingshot the spacecraft from one to the next.

To take advantage of the opportunity, NASA developed the twin Voyager spacecraft. Both would fly by Jupiter and Saturn, adding valuable scientific data to what was then a very scant knowledge of the outer solar system. Ground-based studies revealed the planets’ most basic properties, and hinted that there were fascinating discoveries still to make.

In the early 1970s, Pioneer 10 and Pioneer 11 made the first flybys of the gas giants and their instruments began revealing just how complex those worlds are. With this as the background, Voyager wasn’t just a great opportunity, it was the logical next step is understanding our solar system. Voyager 2, which was actually the first to launch on August 20, 1977, ended up with more opportunities on its trajectory. After flying by Jupiter and Saturn, it would be in the right place to continue its mission and fly by Uranus.

Voyager 1 was a little more limited. Its orientation after flying by Saturn would send it out of the ecliptic, the plane where all the planets orbit the sun. But even without another planetary target, Voyager 1 would keep on going. It would, as the 1977 pre-launch press kit described, continue “outward from the solar system and across the boundary of the wind of charged particles (solar wind) that streams outward from the Sun, thus penetrating into interstellar space.” At the time, there was no concrete plan to keep in touch with the spacecraft after it left Saturn. Source: DNews

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