by Pete Spotts, Staff writer / December 14, 2010
Voyager 1 is about to kiss the solar system goodbye.
The plucky spacecraft – one of two Voyagers launched more than 30 years ago and now bound for interstellar space – appears to have reached a region within a broad boundary between the sun's influence and interstellar space where the speed of the solar wind's outflow reaches zero, scientists report.
The region is known as the heliopause, where the solar wind – a continuous flow of charged particles that streams from the sun in all directions at roughly 1 million miles per hour – is brought to a standstill as it meets interstellar winds head-on and gets deflected sideways.
"The solar wind has turned the corner," said Ed Stone, the mission's project scientist, in a statement. The Voyager team presented its evidence at the fall meeting of the American Geophysical Union, currently under way in San Francisco.
The boundary between the sun's influence, known as the heliosphere, and interstellar space is thought to consist of four onion-like layers: the termination shock, where the solar wind grows increasingly turbulent as the sun plows through interstellar space; the heliosheath, where the wind grows turbulent and get compressed and heated; the heliopause, Voyager 1's current location, and the bow shock, the outermost region where the solar system in essence generates a wake in the tenuous gas and dust between stars.
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http://www.csmonitor.com/Science/2010/1214/Voyager-1-spacecraft-entering-heliopause-leaving-solar-wind-behind