Editing Interstellar medium (section)

===Interaction with interplanetary medium===
The interstellar medium begins where the [[interplanetary medium]] of the [[Solar System]] ends. The [[solar wind]] slows to [[Speed of sound|subsonic]] velocities at the [[termination shock]], 90–100 [[astronomical unit]]s from the Sun. In the region beyond the termination shock, called the [[heliosheath]], interstellar matter interacts with the solar wind. ''Voyager 1'', the farthest human-made object from the Earth (after 1998<ref>{{cite web |url=http://voyager.jpl.nasa.gov/mission/fastfacts.html |title=Voyager: Fast Facts |publisher=Jet Propulsion Laboratory}}</ref>), crossed the termination shock December 16, 2004 and later entered interstellar space when it crossed the [[Heliopause (astronomy)|heliopause]] on August 25, 2012, providing the first direct probe of conditions in the ISM {{harvard citation|Stone|Cummings|McDonald|Heikkila|2005}}.