Voyager 1 and 2, Interstellar Envoys of Humanity, Soldier at 45

today is The 45th anniversary of the launch of Voyager 1, one of humanity’s two iconic twin envoys to the universe. (Its brother, Voyager 2, launched two weeks ago.) Now in the dark, far from interstellar space—more than 10 billion miles from home, where our sun looks like any other bright star—the pair are still studying science. They carry with them the Golden Records, which bear the sounds and symbols of Earth, in case an extraterrestrial ever meets a spacecraft and becomes curious about its distant sender.

“I’ve been following the Voyager trajectory throughout my career,” says Linda Spilker, deputy Voyager project scientist at NASA’s Jet Propulsion Laboratory, who started at the agency in 1977, the year the two probes began. “I am amazed at how long these two spacecraft, Voyager 1 and Voyager 2, have been able to continue to advance and bring back unique science about new places that no spacecraft has visited before. And now they are interstellar travelers. How cool?”

The two car-sized probes, each with a 12-foot antenna mounted on top, had one primary mission: to visit the gas giants of our solar system. After their launch, Voyagers’ paths diverged, but both took advantage of a rare planetary constellation, snapping groundbreaking photos as they flew by Jupiter, Saturn, Uranus and Neptune and revealing tantalizing details about the planets’ moons. By the end of 1989, they had completed this task. In 1990, Voyager 1 was crowned by wrapping and taking you romantic From our world, which is the world of astronomy and science Carl Sagan It’s called pale blue dot.

“Look back at the point. This is here. This house. This is us.” Sagan wrote, “Everyone you love, everyone you know, everyone you ever heard of, and every human ever had lived their life.” A cosmic perspective — just “a speck of dust suspended in a moonbeam,” as he puts it — is almost as unforgettable as Sunrise An image taken by an astronaut on Apollo 8 showing the planet as seen from the moon.

The two probes, which run on nuclear-powered systems called thermoelectric generators (RTGs), continued to fly. Our solar system has no clear boundaries, but in the 2000s they passed the “end shock”, in which particles of the solar wind suddenly slow to subsonic speed due to pressure from gas and magnetic fields in interstellar space. Then in 2010, they breached the solar barrier, the boundary between the solar wind and the interstellar wind.

With four instruments operating on Voyager 1 and five aboard Voyager 2, they now have a new function: measuring magnetic field strength, plasma density, and the energy and direction of charged particles in the environment they are traveling through. “The purpose of the interstellar mission is to measure the effects of the Sun as we move further and further away from Earth. We are trying to figure out how the heliosphere interacts with interstellar space,” says Susan Dodd, Voyager Interstellar Mission Project Manager at JPL. Voyager 1 is currently 14.6 billion miles from home, and Voyager 2 is 12.1 billion miles away, but for perspective, the closest star is about 25 trillion miles away. (NASA maintains their flight tracker.) It’s a brilliant coda for their mission, after decades of probes completing their main objectives.