The Voyager 1 probe was launched into space 40 years ago, but still continues to make discoveries. In 2012, it went beyond the solar system, thus becoming the first interstellar object created by human hands. While studying outer space, the probe recorded a plasma “hum,” the intensity of which turned out to be higher than expected.

It was discovered by the Plasma Wave System (PWS), one of the few that has remained operational over the past 40 years. Earlier, radio waves from Jupiter and Saturn were recorded with the help of it, but the device really showed itself on the border of the heliosphere and beyond.

In interstellar space, the influence of the solar wind is minimal, but the powerful coronal mass ejections of our star are still audible in the monotonous plasma noise like thunderclaps. The discovery of a rather intense activity of electrons in interstellar space was rather fascinating.

The author of the study, Stella Ocker, noted that the hum recorded by the probe is very weak, since it is in a narrow frequency band, but its presence is constant and monotonous.