CNN:

NASA's Voyager 2 probe, launched in 1977, is now more than 11 billion miles from Earth and has reached interstellar space, the agency said Monday. This is the second time a human-made object has reached this part of space. And it's an incredible feat for a spacecraft designed to last five years.

 

Voyager 2 is now NASA's longest-running mission, with 41 years under its belt.
This boundary is where hot solar wind meets cold interstellar space, and it's called the heliopause. Mission scientists compared data from instruments on Voyager 2 to determine that the actual date of the crossing was November 5, when the solar wind particles around the probe dipped greatly, meaning it left the heliosphere.
 
https://voyager.jpl.nasa.gov/galleries/images-on-the-golden-record/
 
This illustration shows the position of NASA's Voyager 1 and Voyager 2 probes outside the heliosphere, a protective bubble created by the sun that extends well past the orbit of Pluto.

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