Illustation of American spacecraft Voyag

After 35 years of careening through space—11.5 billion miles of constant traveling—a man-made object has crossed the threshold into the deepest unknown. Scientists on Wednesday announced new findings that suggest Voyager I has finally left our solar system, beyond the heliosphere and into a vast, dangerous part of space that's never been explored.

When we last heard of the Voyager I's journey, researchers said the probe was traveling through the magnetic highway just before interstellar space. Just a few months later, it's crossed that gateway into a more mysterious reach of gas and stars and we don't even know what else—it's difficult to grasp that space goes on that far. Back in December, scientists said a signal pinged from the Voyager 1 to Earth took 17 hours.

"There's no way of knowing exactly where the solar system ends, but the best guess is that it's up to 14 billion miles from the sun," said TIME's Jeff Kluger in a 2011 piece about the Voyager. Perhaps we'll find out sooner than we think.

In an official statement from the American Geophysical Union (AGU), Bill Weber, professor emeritus of astronomy at New Mexico State University in Las Cruces, provides a full breakdown of how scientists were able to determine—by measuring cosmic ray intensity—that the Voyager I left our crummy old solar system.

The AGU statement does say scientists are still debating whether Voyager 1 did reach interstellar space, or merely a separate, undefined region. Either way, it's outside the normal heliosphere, full of new measurements and unknown possibilities—11.5 billion miles away.