Thirty-six years after the spacecraft Voyager I was launched, it's finally for sure left our solar system and moved on to bigger, more interstellar space, NASA announced today. After scrutinizing data for more than a year, scientists determined that the spacecraft officially left our heliosphere (the bubble of the sun's particles enclosing the solar system) into interstellar space sometime around August 25, 2012.
All of which means that Voyager I, designed by scientists at NASA's Jet Propulsion Laboratory, is the first man-made object to leave the solar system and is therefore the furthest artifact of human civilization in the universe. Cool, right?
Voyager I was launched in 1977 and has now traveled 11.7 billion miles at a speed of 38,000 miles per hour.
Voyager I returned the first-ever detailed photographs of Jupiter and Saturn and their moons. That was in 1980; the project's "primary mission" was now complete. But the craft was also intended to gather data on the boundaries of our solar system -- the Kuiper belt, the heliosphere. And so its journey continued beyond the Jovian and Saturnian systems, recording conditions between planets and occasionally snapping pictures that would induce existential reflection and adorn a dorm room or two, like the famous "Pale Blue Dot" of Earth, taken in 1990 from a distance of 6 billion miles:
That's scientist-sage Carl Sagan on the video, who requested that Voyager be turned around to take a pic of Earth and the other planets for a "Family Portrait." Sagan had a hand in the Voyager project's design, especially the Golden Record, a gold-plated disc that holds a variety of media -- photos of Earth and its inhabitants, audio recordings of famous speeches in different languages, sounds of babies crying and laughing, and a collection of great musical works by the likes of Mozart and Blind Willie Johnson. It's a message from Earth, should an alien intelligence ever stumble across the spacecraft out there.
That's of course an unlikely event; the Record was as much for us as anything.
But Voyager is carrying it out there into the darkness. Scientists discovered that the probe reached interstellar space last year because it was no longer surrounded by ionized gases blown out by our own sun; it is now floating through cool, dense plasma, particles emitted from exploded stars in other systems. The craft was even able to record the sounds of the dense plasma of interstellar space (the sound frequencies represent the plasma's density):
Lead Scientist Edward Stone of the California Institute of Technology, who has been monitoring Voyager's progress since it was launched, expects the spacecraft to continue transmitting data from its journey until at least 2025, when the probe is expected to run out of power.
The Voyager mission will now continue as the craft keeps transmitting data from a realm of which most humans can hardly dream. If it doesn't run into any obstacles, it should send us back our first impressions of what it's like out in space, 36 years from home and 40,000 years from its meeting with the next star.
Watch a video of NASA's announcement from today: