A NASA Probe Launched in 1977 Just Entered Interstellar Space

Now, Voyager 2 has followed it, according to NASA.

Suzanne Dodd, Voyager project manager at NASA's Jet Propulsion Laboratory in California, said: "We're looking forward to what we'll be able to learn from having both probes outside the heliopause".

Voyager 1's Plasma Science Experiment instrument stopped working in 1980, but Voyager 2's instrument is still working and provides unprecedented observations of the passage into interstellar space.

One of the instruments measures solar plasma and this is the first time Nasa has seen a drop in that key instrument. For example, NASA's Interstellar Boundary Explorer (IBEX) that is in Earth orbit is observing the interface between the heliosphere and interstellar space and trying to help astrophysicists understand how the interstellar medium interacts with the heliosphere as our solar system travels through interstellar space.

The probe's present location is some 18 billion kilometres from Earth. They both conducted close-up studies of Jupiter and Saturn.

Each spacecraft carries a Golden Record of Earth sounds, pictures and messages, which aims to serve as evidence of Earth's civilisation.

Voyager 2 is now just over 11 billion miles from Earth. Originally some scientists speculated our star's winds would peter out in the vicinity of Mars, but the Voyager spacecraft have gradually pushed this boundary far beyond. Here are some of the known cosmic landmarks the Voyagers could meet in their relatively near futures.

Voyager 2 launched in 1977, 16 days before Voyager 1, and both have traveled well beyond their original destinations. Until November 5 this year the PLS aboard the Voyager 2 was sending readings with high solar wind levels. At that point, Ross 248 will be the closest star to our sun, briefly eclipsing the Alpha Centauri system's claim to fame as its path through the galaxy brings it just 3.02 light-years away.

Voyager 2 may be freshly interstellar, but it won't be anywhere near another star until 40,000 years from now.

"Inside the bubble, most of the material has come from our sun and the magnetic field has come from our sun", Voyager project scientist Ed Stone explained in a video provided by NASA. For starters, it makes sense to say that the Solar System extends to the edge of the influence of the Sun. It discovered five moons, four rings, and a "Great Dark Spot" that vanished by the time the Hubble Space Telescope imaged Neptune five years later.

At 41 years into its planned 5-year operation, it is now NASA's longest-running mission.

Although neither Voyager's instruments will last forever, the two spacecraft themselves will continue their plodding course across the solar system. Some of these rays get into the heliosphere, but the team expected that spacecraft would detect a slow increase in cosmic rays as it neared the heliopause and then a sudden increase when it crossed over the boundary.

  • Joey Payne