NASA's Voyager 1 became the first spacecraft to enter interstellar space in 2012.
Notes on verification
Confirmed by multiple authoritative sources including NASA, JPL, JHU APL, and Britannica. Physical crossing occurred August 2012, though public confirmation came in September 2013.
Sources
- The biggest scientific breakthroughs of the last 25 years—and ... (nationalgeographic.com)
- https://science.nasa.gov/mission/voyager/interstellar-mission/ (science.nasa.gov)
- https://www.jhuapl.edu/news/news-releases/130912-voyager-1-reaches-interstellar-space (jhuapl.edu)