Voyager's long journey into interstellar space

By Michael J.W. Stickings

NASA launched its Voyager 1 spacecraft on September 5, 1977, the year both Star Wars and Close Encounters of the Third Kind amazed moviegoers on the silver screen. Today, a little over 36 years later, NASA confirmed that the 1,590-pound probe recently left our solar system and entered what is known as interstellar space, the first spacecraft ever to do so:

By today's standards, the spacecraft's technology is laughable: it carries an 8-track tape recorder and computers with one-240,000th the memory of a low-end iPhone. When it left Earth 36 years ago, it was designed as a four-year mission to Saturn, and everything after that was gravy.

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Even among planetary scientists, who tend to dream large, the idea that something they built could travel beyond the Sun's empire and keep grinding away is impressive. Plenty of telescopes gaze at the far parts of the Milky Way, but Voyager 1 can now touch and feel the cold, unexplored region in between the stars and send back detailed dispatches about conditions there. It takes 17 hours and 22 minutes for Voyager's signals to reach NASA’s Jet Propulsion Laboratory here...

The lonely probe, which is 11.7 billion miles from Earth and hurtling away at 38,000 miles per hour, has long been on the cusp, treading a boundary between the bubble of hot, energetic particles around the solar system and the dark region beyond. There, in interstellar space, the plasma, or ionized gas, is noticeably denser.

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At a news conference on Thursday, NASA scientists were a bit vague about what they hope to get from Voyager 1 from now on. The answer, to some extent, depends on what instruments continue to function as the power supply dwindles. [NASA Voyager expert] Dr. [Edward] Stone expects Voyager 1 to keep sending back data — with a 23-watt transmitter, about the equivalent of a refrigerator light bulb — until roughly 2025.

One hope is that Voyager 1's position will allow scientists to more accurately study galactic cosmic rays, which are high-energy particles that originate outside the solar system. They would use the information to make judgments about what interstellar space is like at even greater distances from Earth.

In its heyday, Voyager 1 pumped out never-before-seen images of Jupiter and Saturn. But it stopped sending home pictures in 1990, to conserve energy and because there was no longer much to see. A companion spacecraft, Voyager 2, also launched in 1977, has stopped sending back images as well. Voyager 2 is moving in a different direction but is also expected to exit the solar system.

Eventually, NASA said, the Voyagers will pass other stars, coasting and drifting and being pulled by gravity. The next big encounter for Voyager 1, in around 40,000 years, is expected to be a dwarf star dispassionately known as AC+793888 in the constellation of Camelopardalis.

Amazing. Truly amazing.

Maybe one day someone, or something, will find this humble little creature and bring him home. Either way, whatever its future, Voyager is at the very forefront, literally, of our exploration of space, our first ambassador into the known and unknown that lies beyond our relatively tiny solar home.