Gene Roddenberry’s first Star Trek movie was about the Voyager space probe continuing its mission far beyond what anyone had conceived of. NASA’s Voyager 1 continues to move beyond expectations into what NASA calls our “solar system’s final frontier.”
Voyager heads to the unabridged expanse where the sun has no influence and solar winds pound into the thin gas between stars.
“Voyager 1 has entered the final lap on its race to the edge of interstellar space,” said Dr. Edward Stone, Voyager project scientist at the California Institute of Technology in Pasadena. Caltech manages NASA’s Jet Propulsion Laboratory in Pasadena, which built and operates Voyager 1 and its twin, Voyager 2.
In November 2003, the Voyager team announced it was seeing events unlike any in the mission’s then 26-year history. The team believed the unusual events indicated Voyager 1 was approaching a strange region of space, likely the beginning of this new frontier called the termination shock region. There was considerable controversy over whether Voyager 1 had indeed encountered the termination shock or was just getting close.
The termination shock is where the solar wind, a thin stream of electrically charged gas blowing continuously outward from the sun, is slowed by pressure from gas between the stars. At the termination shock, the solar wind slows abruptly from a speed that ranges from 700,000 to 1.5 million mph and becomes denser and hotter. The consensus of the team is Voyager 1, at approximately 8.7 billion miles from the sun, has at last entered the heliosheath, the region beyond the termination shock.
It was difficult for NASA scientists to gauge where the termination shock was because no one knows for sure the conditions of interstellar space and shifts of speed and pressure of the solar wind cause the dimensions of the termination shock to alter.
The telltale sign seems to be the increase in the magnetic field carried by the solar winds combined with a decrease in speed.
In December 2004, the Voyager 1 dual magnetometers observed the magnetic field strength suddenly increasing by a factor of approximately 2 1/2, as expected when the solar wind slows down. The magnetic field has remained at these high levels since December. NASA’s Goddard Space Flight Center, Greenbelt, Md., built the magnetometers.
Voyager 1 also observed an increase in the number of high-speed electrically charged electrons and ions and a burst of plasma wave noise before the shock. This would be expected if Voyager 1 passed the termination shock. The shock naturally accelerates electrically charged particles that bounce back and forth between the fast and slow winds on opposite sides of the shock, and these particles can generate plasma waves.
“Voyager’s observations over the past few years show the termination shock is far more complicated than anyone thought,” said Dr. Eric Christian, Discipline Scientist for the Sun-Solar System Connection research program at NASA Headquarters, Washington.
Voyager will continue on and no one knows for sure how far the probe will go. One thing is for sure, it will continue to go where no man has gone before.
John Stith is a staff writer for Murdok covering technology and business.
