After covering an average million miles a day for the last 36 years, NASA’s  Voyager 1 has moved beyond the Sun’s heat bubble and become the first manmade craft to move beyond our solar system.

“Scientifically it’s a major milestone, but also historically—this is one of those journeys of exploration like circumnavigating the globe for the first time or having a footprint on the Moon for the first time. This is the first time we’ve begun to explore the space between the stars,” Professor Ed Stone, the chief scientist on the venture, told BBC News. Stone said that the team had launched the Voyager spacecraft over 40 years ago with the hope that it would go into interstellar space.

Voyager was launched back in 1977 with the initial mission of studying the outer planets, but it seemed to have other plans and just kept on going. Today, the NASA mission is almost 12 billion miles from Earth and is moving in the space between the stars.

Scientists have long theorized that the density of charged particles around Voyager-1 would spike if the spacecraft moved beyond the Sun’s particle winds and magnetic fields. To measure this rise, Voyager took readings from a Plasma Wave Science instrument, and readings taken in October/November last year and April/May of this year revealed a 100-fold jump in the amount of protons occupying every inch of space.

The team put together the data and based on its readings confirmed the escape from the solar system occurred around August 25, 2012. “The atmosphere of the sun expands supersonically, a million miles per hour, creating a huge bubble around all the planets that’s called the heliosphere,” Stone said. “And inside that bubble, it’s filled with the wind from the sun, which is (an electrically charged) plasma, and that plasma carries out from the sun the sun’s magnetic field. And that fills this bubble.

“Outside this bubble, the plasma comes from the explosions of other giant stars millions of years ago and that plasma carries with it the magnetic field of the galaxy. So that’s what’s inside. We are now outside.”

Voyager 1’s journey is not over. Its path will place it within about 1.6 lightyears of a star in the Camelopardalis constellation in about 40,000 years. “Certainly luck is an important part of this but wow, when we first saw that data a year ago it was really quite stunning after having been on the way for so many years,” Stone said.