What is the ‘persistent hum’ detected by NASA’s Voyager 1?

11 May 2021

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A ‘persistent hum’ of plasma has been detected by Voyager 1 as it travels through interstellar space.

After launching into space 44 years ago, the NASA Voyager 1 probe has become the most distant human-made object in space – and it’s still going strong.

Now, in a paper published in Nature Astronomy, a team of researchers said a persistent vibrating hum of plasma has been detected by the spacecraft.

Voyager 1 flew past the edge of our solar system almost a decade ago, with NASA confirming its entry to interstellar space in 2014. Now, its instruments have detected the constant drone of interstellar gas, or plasma waves.

Stella Koch Ocker, a doctoral student in astronomy at Cornell University, uncovered the emission. “It’s very faint and monotone, because it is in a narrow frequency bandwidth,” she said. “We’re detecting the faint, persistent hum of interstellar gas.”

James Cordes, senior author of the research and professor of astronomy at Cornell, said the interstellar medium is like a quiet or gentle rain. “In the case of a solar outburst, it’s like detecting a lightning burst in a thunderstorm and then it’s back to a gentle rain.”

What does it mean for science?

The discovery could give scientists an understanding of how the interstellar medium interacts with the solar wind and how the protective bubble of the solar system’s heliosphere is shaped and modified by the interstellar environment.

Ocker also believes that there is more low-level activity in the interstellar gas than scientists had previously thought, which could allow researchers to track the spatial distribution of plasma.

Cornell University research scientist Shami Chatterjee said researchers have never had the chance to continuously track of the density of interstellar space before. “Now we know we don’t need a fortuitous event related to the sun to measure interstellar plasma,” he said.

“Regardless of what the sun is doing, Voyager is sending back detail. The craft is saying, ‘Here’s the density I’m swimming through right now. And here it is now. And here it is now. And here it is now.’ Voyager is quite distant and will be doing this continuously.”

Jenny Darmody is the editor of Silicon Republic