Voyager 1, launched in 1977, is now the only man-made spacecraft that has left the heliosphere (the magnetic field and charged particles around the sun) and entered interstellar space. However, it hasn't left our solar system, and unfortunately won't leave during our lifetimes. Voyager 1 is approaching the Oort Cloud, made up of many comets, and will reach the edge of the solar system in 14,000 to 28,000 years.
It is not a very simple task to determine when Voyager 1 reached interstellar space. Scientists had to do some detective work to determine that the spacecraft was surrounded by higher-density particles that were vibrating after a powerful solar eruption, and that surrounding particles in the heliosphere wouldn't be as dense.
Both Voyager 1 and Voyager 2, its twin spacecraft, have been operational and actively recording information since their launches.
http://news.yahoo.com/confirmed-voyager-1-interstellar-space-171605357.html
It is not a very simple task to determine when Voyager 1 reached interstellar space. Scientists had to do some detective work to determine that the spacecraft was surrounded by higher-density particles that were vibrating after a powerful solar eruption, and that surrounding particles in the heliosphere wouldn't be as dense.
Both Voyager 1 and Voyager 2, its twin spacecraft, have been operational and actively recording information since their launches.
http://news.yahoo.com/confirmed-voyager-1-interstellar-space-171605357.html