More than 35 years after leaving Earth, scientists say the Voyager 1 spacecraft appears to have left our solar system. Astronomers funded by NASA's Jet Propulsion Laboratory today announced their study, reporting that Voyager 1 measured drastic changes in radiation levels — an indication that the spacecraft has left the wind of the Sun's energetic particles behind, traveling into unknown space. In December, scientists observed that Voyager had entered the penultimate stretch of its journey to interstellar space: an area called the "magnetic highway." At the time, NASA predicted that Voyager was anywhere from "a few months to a couple of years away" from leaving the solar system.

Voyagers 1 and 2, launched in 1977 under the Carter administration, were sent to fly to Jupiter, Saturn, and, assuming they could survive long enough, to other planets in the solar system. Voyager 2 successfully reached Neptune in 1989, while Voyager 1 was launched by Saturn's gravity into a new trajectory that has taken it to the edge of our cosmic backyard. While there's no telling when Voyager 1 and 2 will go quiet, they'll still bear marks of human civilization; each spacecraft carries gold-plated disks with representations of photos, music, and messages from Earth. "This is a present from a small distant world, a token of our sounds, our science, our images, our music, our thoughts, and our feelings," said President Jimmy Carter following the Voyager launch. "We hope someday, having solved the problems we face, to join a community of galactic civilizations."

The astronomers note that scientists are still debating whether Voyager 1 has reached interstellar space, but in any event, the spacecraft has reportedly entered an unknown region. "It's outside the normal heliosphere," says New Mexico State University astronomer W.R. Webber. "We're in a new region. And everything we're measuring is different and exciting."

Update: The astronomers involved in today's announcement were right about one thing: the results are under debate. The official Voyager team at NASA has just disputed the findings, saying that "it is the consensus of the Voyager science team that Voyager 1 has not yet left the solar system or reached interstellar space."