Researchers, including a University of York scientist, made a chance discovery when they were studying plasma. They presented evidence showing that stars might make a sound. The study was published in Physical Review Letters.
After shooting high-intensity lasers at plasma, researchers noticed the production of a sound wave. Plasma flowed rapidly from areas of high density to more stagnant regions of low density in such a way that it created something like a traffic jam.
“Plasma piled up at the interface between the high and low density regions, generating a series of pressure pulses: a sound wave,” according to a statement.
The sound generated was at such a high frequency that it would have left even bats and dolphins struggling to hear. The sound had a frequency of nearly a trillion hertz. It was six million times higher than sound which can be heard by any mammal.
A team of scientists included Dr. John Pasley of the York Plasma Institute in the Department of Physics at York. Dr. Pasley worked with scientists from the Tata Institute of Fundamental Research in Mumbai, India, and the Science and Technology Facilities Council’s Central Laser Facility in Oxfordshire.
“One of the few locations in nature where we believe this effect would occur is at the surface of stars. When they are accumulating new material stars could generate sound in a very similar manner to that which we observed in the laboratory – so the stars might be singing – but, since sound cannot propagate through the vacuum of space, no-one can hear them,” said Dr. Pasley.
A numerical model was developed by Dr. Alex Robinson from the Plasma Physics Group at STFC’s Central Laser Facility to produce acoustic waves for the experiment.
“It was initially hard to determine the origin of the acoustic signals, but our model produced results that compared favorably with the wavelength shifts observed in the experiment. This showed that we had discovered a new way of generating sound from fluid flows. Similar situations could occur in plasma flowing around stars,” Dr. Alex said.
This research project was funded by the Engineering and Physical Sciences Research Council and the Tata Institute of Fundamental Research.
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