New and "unexpected" data indicated 36 years after it was launched, Voyager 1 has left the heliosphere, the bubble of hot, energetic charged particles surrounding the solar system, and entered into a region of cold, dark space, known as interstellar space, Xinhua reported citing NASA.
It said the spacecraft arrived in this cold, unexplored interstellar region on or about Aug 25, 2012, and is now about 19 billion km from our Sun.
"Now that we have new, key data, we believe this is mankind's historic leap into interstellar space," Ed Stone, Voyager project scientist based at the California Institute of Technology, said in a statement.
"The Voyager team needed time to analyse those observations and make sense of them. But we can now answer the question we've all been asking -- 'Are we there yet?' Yes, we are," Stone said.
The findings are published in the US journal Science.
Voyager 1 and its twin, Voyager 2, were launched 16 days apart in 1977. Both spacecraft flew by Jupiter and Saturn. Voyager 2 also flew by Uranus and Neptune.
Voyager 2, launched before Voyager 1, is the longest continuously operated spacecraft. It is about 15 billion km away from our Sun. Scientists are not certain when Voyager 2 is expected to cross into interstellar space, but they believe it's not very far behind.