The Rosetta craft uses five instruments in the Rosetta Plasma Consortium (RPC) that provide a wide variety of complementary information about the plasma environment that surrounds the comet.
Plasma is an electrically conductive gas and the RPC is responsible for measuring variations in the comet’s activity, how the comet’s jets of vapor and dust interact with the solar wind, and the structure and dynamics of the comet’s nucleus and plasma ‘atmosphere’.
One observation has surprised RPC scientists, however. The comet seems to be emitting a ‘song’ in the form of oscillations in the magnetic field within the comet’s environment.
It is being sung at 40-50 millihertz, well below human hearing ability, which picks up sound ranging between 20 Hz and 20kHz. To make the music audible to the human ear, scientists have increased the frequencies by about 10,000 times. Here is the result:
The music was first detected in August during a magnetometer experiment when Rosetta was approaching the comet from 100 kilometers (62 miles) away, and it has continued.
Scientists think the oscillations must be produced in some way by the activity of the comet, as it releases neutral particles into space where they become electrically charged due to a process called ionisation. The precise physical mechanism behind the oscillations remains a mystery, however.
“This is exciting because it is completely new to us,” said Karl-Heinz Glaßmeier, head of Space Physics and Space Sensorics at the Technische Universität Braunschweig, Germany. “We did not expect this and we are still working to understand the physics of what is happening.”
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