Scientists of the University of York when examining the interaction of an ultra-intense laser with a plasma target they realized that in the trillionth of a second after the laser strikes, the plasma rapidly flows from high density to low density regions, in such a way that they cause a traffic jam at the interface between low and high density regions generating series of pressure pulses a sound wave
The sound generated was at a high frequency. It was six times higher than what any mammal can hear.
The frequency of nearly trillion hertz, it was the highest frequency possible in such a material
The technique used by the scientist allows them to analyze how the fluid moved when it is struck by a laser; it is just like the police speeding cameras.
The study of fluids in motion is known as hydrodynmaics.
Dr. Pasley one of the scientist said, “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.”
“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.” said Dr. Alex Robinson from the Plasma Physics Group at STFC’s Central Laser Facility who has developed a numerical model to develop acoustics for the experiment.