The Voyager 1 space probe has left the solar system.
After 36 years - and a couple of recent false alarms - Nasa now says that the craft has become the first manmade object to enter inter-stellar space.
Based on data about the hot gas on the edge of our Solar System, scientists can now be sure that the craft left our sun's heliosphere in August 2012.
The Voyager 1 probe was initially launched just to explore the planets of our solar system. But it continued to function beyond its engineers' expectations, and is still transmitting data even now it has left area of our sun's influence.
"Now that we have new, key data, we believe this is mankind's historic leap into interstellar space," said Ed Stone, Voyager project scientist based at the California Institute of Technology, Pasadena.
"The Voyager team needed time to analyze 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."
The remarkably durable craft has now travelled 11 billion miles, trailed at 9 billion miles by its successor, Voyager 2.
Voyager 1 will now travel alone in space, on a course for the star AC +793888 - which it will never reach.
Within 15 years its plutonium generator will stop producing electricity, at which point its transmitter will die and it will drift alone in space.
Nasa's spacecraft recorded drastic changes in radiation levels on August 25, 2012 according to a study in Geophysical Research Letters, a journal of the American Geophysical Union (AGU).
Those changes hinted that the craft had crossed the so-called "heliocliff" where the Sun's wind of energetic particles ceased to be felt.
That the sudden change reflected the true boundary between our solar system and the wider universe was disputed, but Nasa said it is now clear the boundary has been crossed.
Above: Carl Sagan, a scientist who worked on the Voyager 1 probe, describes the final picture of Earth taken by the craft - the Pale Blue Dot