NASA's Voyager 1 detects the eerie hum of interstellar space

The Voyager 1 spacecraft, launched in September 1977, is currently located about 22.7 billion km from Earth

The classic 1979 sci-fi horror film "Alien" was advertised with the memorable tagline, "In space no can hear you scream." It did not say anything about humming. Instruments aboard spacecraft, which nine years ago exited our solar system's outer reaches, have detected a faint monotonous hum caused by the constant vibrations of the small amounts of gas found in the near-emptiness of interstellar space, scientists said. It essentially represents the background noise present in the vast expanse between star systems. These vibrations, called persistent plasma waves, were identified at radio frequencies in a narrow bandwidth during a three-year period as Voyager 1 traverses interstellar space.