Voyager spacecraft rides tsunami wave in interstellar space

The Voyager 1 spacecraft might still be caught what scientists have described as a cosmic “tsunami wave,” a shock wave that first hit the probe in February. You can hear the eerie interstellar vibrations in a video, courtesy of NASA.

NASA’s Voyager 1 spacecraft, launched in 1977, is the first human-made object to reach interstellar space – the space outside our solar system.

Since 2012, The Voyager 1 spacecraft has experienced three tsunami waves in interstellar space. The most recent, which reached the spacecraft earlier this year, is still propagating outward according to new data. It is the longest-lasting shock wave that researchers have seen in interstellar space.

A “tsunami wave” occurs when the sun emits a coronal mass ejection, throwing out a magnetic cloud of plasma from its surface. This generates a wave of pressure. When the wave runs into the interstellar plasma – the charged particles found in the space between the stars – a shock wave results that perturbs the plasma.

Ed Stone is project scientist for the Voyager mission based at California Institute of Technology in Pasadena. Stone said:

The tsunami causes the ionized gas that is out there to resonate – “sing” or vibrate like a bell.

This is the third shock wave that Voyager 1 has experienced. The first event was in October to November of 2012, and the second wave in April to May of 2013 revealed an even higher plasma density. Voyager 1 detected the most recent event in February, and it is still going on as of November data. The spacecraft has moved outward 250 million miles (400 million kilometers) during the third event.

Don Gurnett, professor of physics at the University of Iowa in Iowa City. Gurnett presented the new data Monday, December 15 at the American Geophysical Union meeting in San Francisco. Gurnett said:

Most people would have thought the interstellar medium would have been smooth and quiet. But these shock waves seem to be more common than we thought.

It is unclear to researchers what the unusual longevity of this particular wave may mean. They are also uncertain as to how fast the wave is moving or how broad a region it covers.

The second tsunami wave helped researchers determine in 2013 that Voyager 1 had left the heliosphere, the bubble created by the solar wind encompassing the sun and the planets in our solar system. Denser plasma “rings” at a higher frequency, and the medium that Voyager flew through, was 40 times denser than what had been previously measured. This was key to the conclusion that Voyager had entered a frontier where no spacecraft had gone before: interstellar space.

Bottom line: Voyager 1 might still be caught what scientists have described as a cosmic “tsunami wave,” a shock wave that first hit the probe in February.

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