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Voyager 1, now in interstellar space, hears an ominous hum

Published May 11th, 2021 11:56PM EDT
Image: NASA, ESA, and G. Piotto (Università degli Studi di Padova); Processing: Gladys Kober (NASA/Catholic University of America)

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The vast majority of NASA’s most interesting projects are ones that are fresh and new, like the Perseverance rover and Ingenuity helicopter. As technology advances, NASA can do more and more interesting and revolutionary things, but sometimes decades-old technology can still provide scientists with novel insights, especially when that technology was blasted into space with the sole purpose of getting as far away from Earth as it can.

NASA’s Voyager 1 spacecraft is currently over 14.1 billion miles from Earth. It’s moving at a speed of approximately 38,000 miles per hour and not long ago passed through our solar system’s boundary with interstellar space. Despite that incredible distance, the spacecraft is still able to relay data back to Earth, and new discoveries are still being made. In a new paper published in Nature Astronomy, researchers studying the spacecraft’s data reveal that Voyager 1 can now hear something in interstellar space, and they think they know what it is.

Sound doesn’t pass through the vacuum of space. Sound travels through the air as waves, and if there is no air to act as a medium for those waves to pass through, sound doesn’t travel. Interstellar space is largely a vacuum, but gas can still exist out there, even in areas that appear to be completely empty. In the case of Voyager 1, it’s been picking up the faint hum of plasma waves in the interstellar medium.

The plasma that Voyager 1 is encountering was produced by our Sun, the researchers say. The solar wind that carries gasses for billions of miles is powerful enough to lead to the expulsion of plasma from our solar system. When the Sun blows its top and a solar storm is produced, the plasma can spike, but even when our star isn’t hot and bothered, there’s still a steady and even amount of plasma flowing into space. It’s an interesting finding, and one that researchers weren’t necessarily expecting.

“We’ve never had a chance to evaluate it. Now we know we don’t need a fortuitous event related to the sun to measure interstellar plasma,” Shami Chatterjee, co-author of the new paper, said in a statement. “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.”

If you’re interested in keeping up with the Voyager 1 spacecraft and its twin, Voyager 2, NASA’s Jet Propulsion Laboratory maintains a very useful website that offers real-time data on speed, distance from Earth, and other interesting statistics. You can even see what scientific instruments are still working on each of the probes. It’s pretty awesome.