Voyager 1 is 14 billion miles away and picking up a bizarre cosmic hum… what is it?

In September 1977, Voyager 1 was launched to space on a journey to visit Jupiter and Saturn, before heading out to the stars. NASA’s robotic explorer reached the heliopause — leaving the solar system (by one major standard) — in 2012.

Now, a new study focused on a hum heard by the intrepid space shows this overlooked signal could tell us a great deal about the distant void lying outside our solar system.

Voyager 1 is now over 22.5 billion kilometers (14 billion miles) from Earth, soaring through a diffuse mixture of particles and gas called the interstellar medium. This hum, recorded since 2017, is thought to be the result of plasma waves in this cosmic soup.

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

Two years after launch, Voyager 1 encountered Jupiter in 1979, and Saturn three years later. When the NASA spacecraft raced past the heliopause (a magnetic bubble, driven by the Sun) in August 2012, it was traveling at more than 60,000 KPH (38,000 MPH).