Ancient cosmology held that each of the planetary spheres corresponded to a different note in a universal musical scale. The tones emitted by the planets depended on the ratios of their different orbits in the same way that the length of a lyre-string determines its tone. The music of the spheres was contemplated by many respected philosophers, like Pythagoras, Plato, Pliny and Ptolemy. The English hermetic philospher Robert Fludd devised celestial scales that spanned three octaves, linking sub-planetary elemental worlds to angelic choruses beyond the stars.

Now, in a letter published on December 10th in Astrophysical Journal Letters, researchers report that the Sun's atmosphere is filled with ultrasound-like waves at a frequency of about 100 millihertz - every ten seconds. "At 10-second period, these waves qualify as ultrasound because individual atoms on the Sun experience only a few collisions during the brief passage of each wave, just as with ultrasound here on Earth," says Dr. Craig DeForest, a senior research scientist in the SwRI Space Science and Engineering Division. DeForest found the signature in data collected in January 2003 in the TRACE program.

"These ripples seem to be carrying about 1 kilowatt of power per square meter on the surface of the Sun," says DeForest. "That is similar to the sonic energy you might find coming out of the speakers at a rock concert. Very loud."

Of course, sound cannot travel through the vacuum of interplanetary space. The TRACE spacecraft, in orbit around the Earth, is an ultraviolet telescope trained on the sun. TRACE data shows small fluctuations in the brightness of solar ultraviolet emissions. Solar ultrasound waves are too faint to be seen directly by TRACE. So, DeForest looked for patterns in the background noise of the telescope.

TRACE is the Transition Region and Coronal Explorer mission; it has an open data policy. TRACE data is available to anyone on the web. The intent of the program is to explore the magnetic field in the solar atmosphere; TRACE was launched in 1998 and uses a 30 centimeter apterture telescope with a 1024x1024 CCD collecting images over an 8.5 arc minute square field of view.

The waves or "ripples" are most likely created by the sudden collapse of magnetically induced electric currents (magnetic reconnection) or by lower frequency sound waves that crash like ocean waves as they make their way up from the surface of the Sun. Both of the sources are likely candidates for the source of the solar atmosphere's mysterious extra heat, making the new waves a valuable tool for exploring a decades-old mystery. "By examining these waves more closely, we should be able to discern the source of energy release in the solar atmosphere, just like you can tell by listening whether the car is running in a dark garage," says DeForest. "In both cases, something is releasing energy into the environment, and that release has a recognizable sonic signature."

In this wave diagram (above), which summarizes nearly 1,000 TRACE images, the waves appear as sloped ridges, showing the presence of sound-like waves in the octave between 50 and 100 mHz. The waves travel about 1,000 times the speed of sound on Earth.

As far as I know, science fiction authors have never used a solar-sized mass as a musical instrument. However, sf is replete with other creative examples of instruments; see Isaac Asimov's visisonor or Jack Vance's stimic. Read more about TRACE, the music of the spheres and solar ultrasound.

(This Science Fiction in the News story used with permission from Technovelgy.com - where science meets fiction.)