December 2004 saw the Voyager 1 spacecraft exit our solar system. It was the first manmade object to do so, and has been an unqualified success from its launch date, September 5, 1977. Its sister ship, Voyager 2 has also made it outside the solar system, and in doing so, provided us with invaluable information about our home.
Voyager 2 exited our solar system at a different location, about 10 billion miles away from Voyager 1 and almost a billion miles closer to the sun. As a result, when Voyager 2 crossed the heliosheath boundary, called the solar wind termination shock, it was able to determine our solar system is “squashed” or “dented”– that the bubble carved into interstellar space by the solar wind is not perfectly round.
“Voyager 2 continues its journey of discovery, crossing the termination shock multiple times as it entered the outermost layer of the giant heliospheric bubble surrounding the Sun and joined Voyager 1 in the last leg of the race to interstellar space.” said Voyager Project Scientist Dr. Edward Stone of the California Institute of Technology, Pasadena, Calif.
All stars expel solar wind, a thin gas of electrically charged particles, pushing away from the star in all directions. These winds eventually carve a bubble around our solar system, outside the range of Pluto, called the heliosphere. As Voyager 1 crossed the termination shock, it began to encounter the resistance from interstellar space, which pushes back against the bubble.
However Voyager 2’s crossing of the termination shock was even more important, even though it was the second one across the line. Unlike Voyager 1, Voyager 2 has a working Plasma Science instrument that can directly measure the velocity, density and temperature of the solar wind. That Voyager 1’s version of this instrument failed back in 1990, caused some questions as to exactly when it crossed the termination shock.
With Voyager 2’s working though, it was able to send back multiple sets of information, as it crossed multiple shocks. Just like the waves of a beach, constantly rolling in over the sand, so the interstellar winds roll across the solar winds. Voyager 2 is now on the other side of this though, just as someone who has paddled outside the breaking waves.
"The important new data describing the termination shock are still being pondered, but it is clear that Voyager has once again surprised us," said Dr. Eric Christian, Voyager Program Scientist at NASA Headquarters, Washington.
Joshua Hill, a Geek’s-Geek from Melbourne, Australia, Josh is an aspiring author with dreams of publishing his epic fantasy, currently in the works, sometime in the next 5 years. A techie, nerd, sci-fi nut and bookworm.
