May 31, 2013
For most people, the study of astrophysics means poring over calculations, charts, texts and graphics. But Wanda Diaz-Merced, a graduate student at the University of Glasgow, and fellow researcher Gerhard Sonnert have pioneered a different approach. Its underlying motif is simple: Space produces music.
She grew up with an enthusiasm for science and space, but in her early 20s, as a physics student at the University of Puerto Rico, her vision swiftly deteriorated due to diabetes. When she spent time in an astrophysical observatory, though, and inadvertently heard the hiss and pops of the signals collected by a radio telescope, she realized that there might be a way she could rely solely on her hearing to interpret data.
Since, she’s teamed with computer scientists to use NASA-developed software called xSonify—which converts scientific data of all kinds into synthesized musical sounds, a process called sonification (PDF)—to analyze solar flares on the sun, as well as X-rays coming from the EX Hydrae star system. This software allows users to customize how the data are represented, using pitch, volume, rhythm and even different types of instruments to distinguish between different values and intensities in the electromagnetic spectrum detected by spacecraft over time.
Diaz-Merced listens to these data streams to pick out irregularities and changes in the sounds, and has even convinced some colleagues to adopt the software, because listening while watching data in chart form can help them become more attuned to subtle patterns in the data. “I can listen for harmonics, melodies, relative high- and low-frequency ranges,” she told Physics Today last year. In one case, she said, “I was able to hear [previously overlooked] very low frequencies from gamma-ray bursts. I had been listening to the time series and said to the physicists in charge, ‘Let’s listen to the power spectra.’”
In its raw form, the sounds she listens to seem more like noise than music:
In the spring of 2011, Diaz-Merced was interning at the Harvard-Smithsonian Center for Astrophysics, in Cambridge, when her use of sonification inspired Gerhard Sonnert, a researcher, to do something new with the sounds. He spotted sheet music that represented X-ray emissions from EX Hydrae, collected by the Chandra X-ray Observatory satellite, and noticed a rhythm, common in Afro-Cuban music, called a clave.
A bass player, Sonnert got the idea to convert the sounds from EX Hydrae, some 200 light-years away, into blues, jazz and classical music. As part of the Star Songs project, he teamed with his cousin Volkmar Studtrucker, a composer, to manually convert the data into nine different songs, which the duo then performed with drummer Hans-Peter Albrecht and released as an album.
Listen to the raw sound data that produced the blues track, along with the completed song:
Studtrucker started off by picking select portions of the signal that were suitable for use in composition. As a whole, the sounds are largely irregular, because they result from X-rays emitted in a variable fashion due to the nature of EX Hydrae. The system is actually made up of two stars, with one continually pulling matter away from the other at varying rates, which causes the level of X-ray emissions to fluctuate as well.
But particular portions of the sounds representing the X-ray emissions seemed to have melodies and a beat, and by repeating these short segments—and adding harmonic elements, as well as altering the underlying clave rhythm—Studrucker was able to compose songs based off the data in a variety of styles. In addition to blues, he produced several others:
Jazz Waltz (data, then song):
Of course, there’s an element of abstraction in all these tracks, and with even the raw sounds produced by xSonify that Diaz-Merced uses to conduct her research. But that doesn’t mean that her research—or Studtrucker’s music—is any less representitive of phenomena in space than the work of conventional astronomers.
As Ari Epstein put it in a terrific Studio 360 segment on Diaz-Merced’s research, “Stars and planets don’t give off sounds as they move through the sky. But they don’t draw lines on graphs either. All of these things—graphs, numbers, music—they’re all just tools we can use to understand a complicated universe.”
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