May 24 2005
From The Space Library
NASA announced that scientists had finally agreed that Voyager 1, launched in 1977, had reached the solar system's final frontier, passed through the termination shock region~the point at the edge of the solar system where the solar wind slows abruptly, and entered the heliosheath~a frontier of unknown thickness defining the border with interstellar space. In November 2003, the Voyager team had announced unusual events in the mission's history, signaling that Voyager 1 had reached the edge of the solar system. However, scientists disagreed as to whether the craft had actually encountered termination shock or was merely approaching the region at the edge of interstellar space. NASA explained that scientists had based the evidence that Voyager 1 had encountered termination shock on the craft's measurement of a sudden increase in the strength of the magnetic field carried by the solar wind, combined with an inferred decrease in speed, which happens when the solar wind slows down. Additionally, Voyager had observed an increase in the number of high-speed, electrically charged electrons and ions, as well as a burst of plasma-wave noise, which scientists had expected to occur when Voyager 1 passed the termination shock. Eric Christian, Discipline Scientist for the Sun-Solar System Connection Research Program at NASA Headquarters, remarked that Voyager's observations over the past few years had shown that termination shock is far more complicated than previously thought. When Voyager 1 entered the heliosheath, the craft was 8.7 billion miles (14 kilometers) away from Earth, the farthest any human-made object had traveled. (NASA, “Voyager Spacecraft Enters Solar System's Final Frontier,” news release 05-131, 24 May 2005, http://www.nasa.gov/home/hqnews/2005/may/HQ_05131_Voyager_agu.html (accessed 14 September 2009); Guy Gugliotta, “Voyager at Edge of Solar System,” Washington Post, 25 May 2005.)
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