Today, it was announced that Voyager 1 has left the solar system for interstellar space.
It’s not the first time the announcement has been made.
In October 2012, it was thought the intrepid probe, first launched in September 1977, had blasted out of the heliosheath and left the solar system—until a couple of months later, when particles weren’t quite acting as scientists thought they should in a region that came to be called the “magnetic highway”—the outer boundary of the heliosphere, where the sun’s magnetic particles and those from interstellar space mingle, not unlike a two-lane highway.
Scientists had thought two things would happen when Voyager officially left the solar system: That the solar winds would fade to nothing (which happened), and that the magnetic fields of the region would change direction marking the end of the sun’s influence. That one didn’t happen.
In recent months some scientists have been reassessing the data and saying “Yes, it might have left the solar system after all.” Now, NASA has confirmed that.
The whole debate was enough of a headache to get a nice ribbing from former JPL employee turned XKCD cartoonist Randall Munroe.
The Future of Interstellar Space Travel
Voyager 1 is now the first craft to officially leave the solar system, pacing along at 38,610 miles per hour. Others are set to follow.
Voyager 1's sister craft, Voyager 2, is not yet beyond the solar system, but is just a few years behind, traveling at a more sluggish crawl of around 35,000 MPH.
Two other probes, Pioneer 10 and 11, will also leave the solar system someday. Pioneer 10 was reported to have left by the New York Times in 1983—except it was just past the orbit of Neptune at the time. Pioneer 11 accomplished this feat in 1990. But as the Voyagers have revealed, that is far, far shy of the end of the solar system.
Currently, Voyager 1 is more than 125 times the distance (called an AU, or astronomical unit) from the Earth to the Sun. Pioneer 10 is far behind that, projected at 109 AU in 2012. Communication was lost in 2003. Voyager 2 is still active, and is approximately 103 AU out. Pioneer 11, which NASA lost contact with in 1995, is estimated to be at 86 AU as of 2012.
We’d of course be remiss not to mention New Horizons, the craft currently on a trajectory for Pluto, which it will swoop by in 2015 before continuing on to the outer solar system. Thus far, it’s only about 27 AU out from the sun. It is expected to leave the solar system in 2029. A booster rocket of the craft is also on a path set to exit the solar system.
Little Green Men
With some push from Carl Sagan, both Voyager probes were given a “Golden Record,” a phonograph of words and images meant to tell aliens of existence here on earth, should the probes be found. Classical music melds with sounds of nature and a series of hellos in various languages on the disc.
Included in the music selections? “Johnny B. Goode” by Chuck Berry.
The Pioneers contain simple plaques, showing two naked humans, the position of the solar system in relation to a group of stars, and the location of the Earth within the solar system. (Prior to Pluto’s demotion, of course.)
Speaking of Pluto, New Horizons doesn’t have an equivalent to either on board. There are a few objects on board, though, which might pique the interest of the discoverers, even if they’ll have no way to tell what they are. Included is a CD with the names of 400,000 persons, as well as the ashes of Clyde Tombaugh, the astronomer who first discovered Pluto in 1930. A Florida state quarter and a scrap of SpaceShipOne are among the few other personal effects on the craft.