Voyager I and II, the two farthest reaching human space probes, are reaching 40 years of exploration this August and September. Originally intended to be operational for four years, the Voyager I and II are nearing the outer edges of the solar system and still communicating with NASA.

At almost eleven billion miles from Earth, the ‘Golden Record’-carrying spacecraft are traveling past our solar system and currently sending back information about cosmic rays and other phenomenon prevalent in interstellar space.

“I believe that few missions can ever match the achievements of the Voyager spacecraft during their four decades of exploration,” said associate administrator for NASA’s Science Mission Directorate Thomas Zurbuchen. “They have educated us to the unknown wonders of the universe and truly inspired humanity to continue to explore our solar system and beyond.”

Launched in 1977, Voyager II is the only spacecraft to have flown to all four outer planets (Jupiter, Saturn, Uranus, and Neptune).

Next stop? Alpha Centauri.

ETA? Unfortunately, it will be a while before Voyager gets to our neighboring star system. According to NASA, it will take another 40,000 years to reach the Alpha Centauri system. That’s because the universe is big and mostly empty. It took 40 years for Voyager I and II to leave our region of space.

There may not be much between solar systems, but scientists are learning a great deal, including how to maximize Voyagers’ life spans. Since the spacecrafts’ power decreases by four watts per year, engineers are having to figure out how to operate them under ever-tighter power constraints.

The Voyager crafts’ mission is still to venture into unexplored space and help us further our understanding of the galaxy.

God speed, Voyager I and II.