Voyager probes approach solar system edge

Super cool space news!  (Compare this artist's rendering with my entry on December 20, 2007.)  I know it's dopey, but when the Voyager probes are in the news, I always think of the first Star Trek movie, which imagined a Voyager probe that returns, still seeking information.

Voyager on the cusp of entering interstellar space


Plowing through the solar system's unexplored frontier, NASA's Voyager 1 spacecraft has entered a region of stagnant solar wind and magnetic pressure and is on the precipice of crossing over into interstellar space. But estimates for when the nuclear-powered probe will break through are not precise. Ed Stone, Voyager's project scientist, said it could be any time between a few months and a few years from now.

"I can almost assure you that will be confused when this first happens because this will not be simple," Stone said. "Nature tends to be much more creative than our own minds."

Moving around the perimeter of the Milky Way galaxy, the sun generates a wind of charged particles moving out in all directions. Ahead of the sun, the solar wind is compressed like the waves in front of a moving ship by a steady flow of plasma emanating from outside the solar system. The solar particles are mostly diverted down and up, then behind the sun like a ship's wake or a comet's tail.

The region of the sun's influence, in which the solar wind is dominant, is called the heliosphere. The heliopause is the boundary between the heliosphere and interstellar space.

No spacecraft has ever left the solar system before, so Voyager 1 is flying through an uncharted void between the influence of the sun and the interstellar wind, which blows waves of plasma and charged particles at a clip of up to 15 miles per second.

"That transition may not be instantaneous," Stone said. "It may take us months to get through a rather messy interface between these two winds."