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First Images of Solar System's Invisible Frontier
FiReaNGeL writes an unexpected side-effect from NASA's STEREO spacecraft has allowed scientists to see a much more well-defined picture of the boundary of our solar system. "The twin STEREO spacecraft were launched in 2006 into Earth's orbit about the sun to obtain stereo pictures of the sun's surface and to measure magnetic fields and ion fluxes associated with solar explosions. Between June and October 2007, however, the suprathermal electron sensor in the IMPACT (In-situ Measurements of Particles and CME Transients) suite of instruments on board each STEREO spacecraft detected neutral atoms originating from the same spot in the sky: the shock front and the heliosheath beyond, where the sun plunges through the interstellar medium."
Meh. It doesn't even recurse like GNU's Not Unix.
What a fool believes, he sees, no wise man has the power to reason away.
Interstellar space isn't empty. You have nebula and lots of (hundreds of billions?) stars spewing particles just like the Sun does, etc. So there is something for the solar wind to run into.
c = (k p / Ï)^1/2
Put in the numbers and get your answer. The speed of sound in space works out to around 300 m/s in these parts.
Or were you under the impression that sound isn't transmitted in space? Sound we can hear isn't, but the ambient gas in space certainly does transmit disturbances, and will let you know if something passing through it exceeds the speed of sound by forming a shock wave.