Voyager I, launched during the first year of Jimmy Carter’s presidency, may have exited the solar system.

“Have humans ventured, for the very first time, into the vast unknown of interstellar space?” the Houston Chronicle‘s Eric Berger asked on his blog. “The Voyager 1 probe is now more than 11 billion miles from Earth. … No man-made object is further away.”

Nick Suntzeff, a Texas A&M astronomer, told Berger that, according to NASA measurements, in the last month the number of “energetic particles” hitting the spacecraft has jumped up, which likely means it is being hit by cosmic rays.

“This probably means that Voyager 1 has left the solar system officially, in that it is no longer protected by the solar magnetic field, and is now totally open to whatever space throws at it,” Suntzeff told Berger.

If these readings are accurate, this puts the spacecraft a little ahead of schedule, as NASA had been estimating it would leave the solar system behind in 2014, Tom Spears reported at the Ottawa Citizen. 

In late May, Wired‘s space blogger and historian David S. F. Portree pointed out that Voyager I is now so far away that radio signals take sixteen hours to reach it.