Never before has a human-built spacecraft traveled so far. NASA's Voyager 1 probe has now left the solar system and is wandering the galaxy, US scientists said today.
The spacecraft was launched in 1977 on a mission to explore the outer planets of our solar system and to possibly journey into the unknown depths of outer space.
"This is the first time that humanity has been able to step outside of the cradle of the solar system to explore the larger galaxy," Marc Swisdak, an astrophysicist at the University of Maryland, told AFP.
The precise position of Voyager has been fiercely debated in the past year, because scientists have not known exactly what it would look like when the spacecraft crossed the boundary of the solar system -- and the tool on board that was meant to detect the change broke long ago.
However, US space agency scientists now agree that Voyager is officially outside the protective bubble known as the heliosphere that extends at least 13 billion kilometers beyond all the planets in our solar system, and has entered a cold, dark region known as interstellar space.
Their findings -- which describe the conditions that show Voyager actually left the solar system in August 2012 -- are published in the US journal Science.
"Voyager has boldly gone where no probe has gone before marking one of the most significant technological achievements in the annals of the history of science," said a statement by John Grunsfeld, NASA's associate administrator for the Science Mission Directorate.
The twin spacecraft, Voyager 1 and Voyager 2, were launched in 1977 on a primary mission to explore Jupiter and Saturn.
They discovered new details about the nature of Saturn's rings and found volcanoes on Jupiter's moon Io.
Voyager 2 traveled on to Uranus and Neptune, before the duo's mission was extended to explore the outer limits of the Sun's influence.
Voyager 1 -- with Voyager 2 a few years behind in its travels to the edge of the solar system -- sent back data to scientists on Earth on August 25 last year, showing an abrupt drop in energetic charged particles, or cosmic rays, that are produced inside the heliosphere.
Scientists expected that the direction of the magnetic field in space would reverse at the barrier known as the heliopause.
The Voyager 1 magnetometer did not show this change, leading scientists to be extra cautious about declaring whether or not the spacecraft had left the solar system.
