NASA has recently released an eerie recording that represents real sound waves rippling through the hot gas and plasma of the Perseus galaxy cluster, located about 250 million light-years away from Earth.
This unsettling audio isn’t science fiction — it’s rooted in a fascinating cosmic phenomenon. A mysterious blinking source, known as GPM J1839–10, has been pulsing in space every 21 minutes since at least 1988. And despite decades of observation, scientists still don’t know exactly what it is.
Many people assume space is silent, and for the most part, they’re right. Because space is a vacuum, there’s typically no medium for sound to travel. However, the Perseus galaxy cluster is so filled with gas that actual sound waves can move through it.
These sound waves were first detected in 2003 using NASA’s Chandra X-ray Observatory. But until now, they’ve never been shifted into the audible range of human hearing. Naturally, these waves exist at a frequency 57 octaves below middle C — far too low for our ears to detect. To make them audible, scientists had to raise the pitch quadrillions of times. The result? A bone-chilling cosmic growl that wouldn’t feel out of place on a Halloween soundtrack.
This effort is part of space sonification — a method of turning astronomical data into sound. It offers a unique way to explore the universe and may help unlock more of its secrets. As we continue venturing deeper into the cosmos, we’re likely to hear more of these alien melodies — each telling us something new about the vast unknown.
Voyager 1: Listening to the Echoes of Interstellar Space
In interstellar space — the vast, sparse region beyond our Sun’s protective bubble — NASA’s Voyager 1 has detected an ongoing “hum” of plasma waves, offering an unprecedented glimpse into this alien frontier.
For decades, all space missions stayed within the heliosphere — a magnetic shield generated by the Sun. That changed on August 25, 2012, when Voyager 1 crossed the boundary and became the first human-made object to enter interstellar space.
Now, years into this new territory, Voyager 1 is recording persistent waves in the thin gas and plasma — a departure from the short bursts it detected before. It’s like a lone raft drifting through cosmic tides, sensing every ripple as it moves away from the Sun’s influence.
A 2018 graphic illustrates the relative positions of Voyager 1 and Voyager 2. While Voyager 1 ventured beyond the heliosphere in 2012, Voyager 2 followed in November 2018. These probes are humanity’s deepest eyes and ears in space.
According to Stella Ocker, a Cornell University Ph.D. student and part of the Voyager team, the spacecraft’s latest findings may represent the first continuous measurement of interstellar plasma density ever recorded. Her study, published in Nature Astronomy, details a consistent tone in the data that subtly changes over time — a sign of varying electron density in the interstellar medium.
Despite its name, the “interstellar medium” isn’t a calm, empty void. It’s filled with turbulent waves — some caused by galactic rotation, others by ancient supernovae or solar storms. These waves shake electrons in space, and the frequency of their “ringing” reveals how densely packed those electrons are. Voyager 1’s Plasma Wave Subsystem — with its signature 30-foot-long “bunny ear” antennas — was designed to pick up this ringing.
In November 2012, just months after entering interstellar space, Voyager 1 captured its first plasma wave signal. Another, louder one followed six months later. These “whistles” have since appeared about once a year, providing rare but valuable data points.
Hoping to fill in the gaps, Ocker searched for a more stable signal — and she found one in mid-2017. This soft, almost single-tone frequency steadily changed over time, closely mirroring the behavior of those earlier whistles. She dubbed it a plasma wave emission, and it offers an exciting new tool for mapping interstellar density.
Over time, Voyager 1 recorded a 40-fold increase in electron density, stabilizing by 2015. That consistent trend has remained through 2020, providing the most comprehensive picture yet of this distant environment.
Researchers are now working on models to understand how this emission is produced — a crucial step in interpreting what Voyager 1 is telling us. In the meantime, the spacecraft continues its journey, drifting deeper into the cosmic unknown and sending back data that could redefine our understanding of space itself.
Want to know more?
Read: “In the Emptiness of Space 14 Billion Miles Away, Voyager I Detects ‘Hum’ From Plasma Waves” for a deeper dive into these discoveries.
The Voyager missions, operated by NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, are part of the NASA Heliophysics System Observatory. These iconic spacecraft continue to carry humanity’s curiosity far beyond the edge of the solar system.
