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ICMYI: A 2nd U.S. spacecraft is now exploring interstellar space. Both launched probably before you were born.

  • 4 min to read
  • NASA announced the Voyager 2 probe has left our solar system. Its twin, Voyager 1, made this historic crossing in 2012.
  • And they're both still talking to us, 41 years after launching into space.
  • Voyager 2 has already logged more than 18.5 billion miles (30 billion kilometers) on its interstellar trip going 34,191 mph (55,025 kph).
  • Next stop: Oort Cloud. It will take about 300 years for Voyager 2 to reach the inner edge of the Oort Cloud and possibly 30,000 years to fly beyond it.
  • But scientists expect to learn a few more things along the way.

NASA's Voyager 2 is now the second human-made object to zip away from the sun into the space between the stars.

Voyager 2 last month exited "this bubble that the sun creates around itself," longtime NASA mission scientist Ed Stone said Monday. The spacecraft is now beyond the outer boundary of the heliosphere, some 11 billion miles (about 18 billion kilometers) from Earth.

It's trailing twin Voyager 1, which reached interstellar space in 2012 and is now 13 billion miles (21 billion kilometers) from Earth. Interstellar space is the vast mostly emptiness between star systems.

Even though they are out of the sun's bubble, the Voyagers are still technically in our solar system, NASA said. Scientists maintain the solar system stretches to the outer edge of the so-called Oort Cloud. It will take about 30,000 years for the spacecraft to get that far.

Scientists know that Voyager 2 has left the sun's influence because of four different instruments that are measuring solar particles and different types of rays. They showed a dramatic change on Nov. 5, indicating the spacecraft was now in between the stars. One of the instruments measures solar plasma and this is the first time NASA saw a drop in that key instrument; the same instrument wasn't working on Voyager 1.

The twin Voyagers launched from Cape Canaveral, Florida, in 1977, and zipped by Jupiter, Saturn, Uranus and Neptune. Voyager 2 has already logged more than 18.5 billion miles (30 billion kilometers) on its interstellar trip going 34,191 mph (55,025 kph).

"Both spacecrafts are very healthy if you consider them senior citizens," Voyager project manager Suzanne Dodd said.

She said the probes should last at least five, maybe 10 more years, but the cold — the temperature outside the vehicles is about 49 degrees below zero (minus 45 Celsius) — and waning power supply will eventually end their usefulness.

Yet the two Voyagers will keep travelling and in 40,000 years or so they'll get close to the next stars, or actually the stars, which are moving faster, will get close to them, Stone said.

While the probes have left the heliosphere, Voyager 1 and Voyager 2 have not yet left the solar system. The true boundary of the solar system is considered to be beyond the outer edge of the Oort Cloud, a collection of comets and small objects that are still under the influence of the Sun's gravity. It will take about 300 years for Voyager 2 to reach the inner edge of the Oort Cloud and possibly 30,000 years to fly beyond it.

Do these things run on batteries?

The Voyager probes are powered using heat from the decay of radioactive material, contained in a device called a radioisotope thermal generator (RTG). The power output of the RTGs diminishes by about four watts per year, which means that various parts of the Voyagers, including the cameras on both spacecraft, have been turned off to manage power.

"I think we're all happy and relieved that the Voyager probes have both operated long enough to make it past this milestone," said Suzanne Dodd, Voyager project manager at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California.

What's the story on these spacecraft?

Voyager 2 launched in 1977, 16 days before Voyager 1, and both have traveled well beyond their original destinations. The spacecraft were built to last five years and conduct close-up studies of Jupiter and Saturn.

However, as the mission continued, additional flybys of the two outermost giant planets, Uranus and Neptune, proved possible. As the spacecraft flew across the solar system, remote-control reprogramming was used to endow the Voyagers with greater capabilities than they possessed when they left Earth.

Their two-planet mission became a four-planet mission. Their five-year lifespans have stretched to 41 years, making Voyager 2 NASA's longest running mission.

"There is still a lot to learn about the region of interstellar space immediately beyond the heliopause," said Ed Stone, Voyager project scientist based at Caltech in Pasadena, California.

Together, the two Voyagers provide a detailed glimpse of how the heliosphere of our solar system interacts with the constant interstellar wind flowing from beyond. "Voyager has a very special place for us," said Nicola Fox, director of the Heliophysics Division at NASA Headquarters. "To have the Voyagers sending back information about the edge of the Sun's influence gives us an unprecedented glimpse of truly uncharted territory."

Is this real? I thought Voyager was a Star Trek episode.

Nice job Trekkie! In the 2270s ("Star Trek: The Motion Picture"), "V'ger" returns as a massive entity threatening Earth with destruction. Turns out, V'ger is the remnant of an unmanned deep space probe launched by NASA in the 20th century.

In the movie, the Voyager probe had been rebuilt by an unknown race of machine entities in order to help it complete what its nameplate said was its primary programming: "learn all that is learnable," and return that knowledge to its creator on Earth. Machines being machines, things went kinda buggy and the new V'ger became bent on exterminating humans and pretty much anything else that got in the way of learning.

Fanboys: Yes, this was similar to a 1960s original Trek episode as well, called "The Changeling." The episode anticipated the launch of Pioneer 10, which eventually became the first of five artificial objects to achieve the escape velocity that have allowed them to leave the Solar System.

Pioneer 10 stopped talking to us in 2003. Let's hope that's just because its radioisotope power source has decayed, and not because it's on the way back with immeasurable defensive, sensory and destructive capabilities -- and a hankering to find its Earthbound creator.