Behind the scenes of ‘The singing comet’

Last month, shortly before Rosetta released Philae to land on Comet 67P/C-G, we posted an article on this blog titled “The singing comet”. It presented an audio track based on data collected with one of the instruments from the Rosetta Plasma Consortium (RPC) on board the orbiter. Perhaps because it added a new layer to the Rosetta story, by engaging another of our human senses to the immersive experience of “being there” at the comet with the spacecraft, this ‘song’ became a worldwide sensation. By now, it has been listened to more than 5.6 million times on SoundCloud. But what does this ‘music’ mean, and how is it possible to ‘record’ sounds in space at all? Readers of this blog have asked a number of questions about “The singing comet”, so we’ve written this post to provide some more details about the production of this unusual audio track. “Clearly, there is no sound as we know it, because acoustic waves need a medium to propagate through, such as an atmosphere, whereas the (almost) empty space around the comet does not allow for that,” explains RPC principal investigator Karl-Heinz Glaßmeier from the Technische Universität Braunschweig, Germany. “But there is another type of wave that can propagate in the tenuous mixture of charged particles and ions, or plasma, present in the comet’s environment. These magneto-acoustic waves are caused by the interaction of the local plasma around the comet with the magnetic field carried by the solar wind, a stream of electrically charged particles blown by the Sun,” says Karl-Heinz. While probing the magnetic environment of the comet, the magnetometer on Rosetta (RPC-Mag) detected these waves as very regular oscillations in the local magnetic field. At only a few nanotesla, this field is very weak, roughly a million times less than from a […]



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