Sunday, August 05, 2012

Voyager 1: Not Quite There Yet

The above image is an artist's concept, showing 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

NASA's Voyager 1 spacecraft is near interstellar space, but is not quite there yet. Two of three key signs of changes expected to occur at that boundary have changed faster than at any other time in the last seven years, according to new data from NASA's Voyager 1 spacecraft.


For the last seven years, Voyager 1 has been exploring the outer layer of the bubble of charged particles the sun blows around itself. In one day, on July 28th, data from Voyager 1's cosmic ray instrument showed the level of high-energy cosmic rays originating from outside our solar system jumped by five percent. During the last half of that same day, the level of lower-energy particles originating from inside our solar system dropped by half. However, in three days, the levels had recovered to near their previous levels.


A third key sign is the direction of the magnetic field, and scientists are eagerly analyzing the data to see whether that has, indeed, changed direction. Scientists expect that all three of these signs will have changed when Voyager 1 has crossed into interstellar space. A preliminary analysis of the latest magnetic field data is expected to be available in the next month.


Project scientists are certain Voyager 1 is in a region of space where things are changing rapidly. But they are not yet able to say that Voyager 1 has officially left our solar system and entered interstellar space.
The levels of high-energy cosmic ray particles have been increasing for years, but more slowly than they are now. The last jump — of five percent — took one week in May. The levels of lower-energy particles from inside our solar system have been slowly decreasing for the last two years. Scientists expect that the lower-energy particles will drop close to zero when Voyager 1 finally crosses into interstellar space.


Voyager 1 was launched on September 5, 1977 and is currently 11 billion miles (18 billion kilometers) from the sun. Voyager 2, which launched on August 20, 1977, is close behind, at 9.3 billion miles (15 billion kilometers) from the sun.  Both spacecraft are healthy as they approach the 35th anniversary of their launch. The project team members know the Voyagers will cross into interstellar space. It's just a question of when.


And now, the mission particulars...

The Voyager spacecraft were built by the Jet Propulsion Laboratory (JPL) in Pasadena, California, which continues to operate both. JPL is a division of the California Institute of Technology (Caltech). The Voyager missions are a part of the NASA Heliophysics System Observatory, sponsored by the Heliophysics Division of the Science Mission Directorate in Washington.


To learn more about the Voyager spacecraft, visit: www.nasa.gov/voyager .


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