By connecting a loudspeaker to a radio telescope it is possible to transform radio signals into sound. Now the new frontier is to sonify one of the most sensational and elusive phenomena: gravitational waves. Astrophysics Patrizia Caraveo writes about it in this article published yesterday in Sole24Ore, here reproduced with the author’s consent
In the cosmic void, sounds cannot propagate. Yet celestial objects sing or, more correctly, vibrate and we, after having registered these vibrations, can transform them into sounds. Inside the Sun, sound waves are reflected by the layers that make up our star. Each reflection leaves a small signature and this is how, by studying the vibrations at different frequencies, we can understand what happens in the depths of our star. It is a different way of penetrating the intimacy of the Sun, made possible by the space probes that keep it under constant control. In addition to having a great scientific value, the data can also have an unexpected artistic value. NASA created Solarium, a multimedia show where the high-resolution images of the ever-boiling surface of the Sun envelop the viewer while the sonification of the vibrations makes us feel its internal music.
The sonification process is easily applied to all cyclic phenomena, because the periodicities immediately transform into sound frequencies. The idea is certainly not original. Interpreting the rhythmic motions of the planets in music was, perhaps, a pastime of Pythagoras. Certainly Kepler applied to it and wrote a treatise entitled Harmonices Mundiwhere he makes each planet correspond to a geometric solid and a musical harmony. If you want to get an idea of the procedure, I recommend watching the video at the bottom of this article: you will see that each planet is described by a sequence of notes with duration proportional to its orbit. We gradually move from the farthest, slowest and lowest sounds (Saturn and Jupiter) to the nearest, faster planets with the highest sounds.
Kepler wanted to make people appreciate the harmony of creation, but his idea is a beautiful example of the sonification of the Solar System at the basis of the concept of the music of the spheres. By connecting a loudspeaker to their telescopes, radio astronomers transform the signals they receive into sound. Let us consider the case of neutron stars. These are corpses of stars that rotate very quickly around their axis and produce radio signals thanks to a process that concentrates the emission inside a thin cone that is formed by virtue of their very high magnetic field. These characteristics make neutron stars similar to the coastal lighthouses that, since the dawn of time, have guided sailors. Each lighthouse has its own rotation frequency, just as each neutron star has its own periodicity. Each star is different from the others and is easily recognizable from its song. Those that go one revolution per second resemble the ticking of an old alarm clock. The neutron star in the Sails constellation has a period of 89 ms, so it makes 11 rotations per second and looks like a diesel engine. If the idea of a celestial object with a mass similar to that of the Sun that rotates 11 times per second seems difficult to imagine, think that the most hasty neutron stars rotate 800 times per second, making both Formula engines pale. 1 and those of the Moto Gp.
These are interesting experiments applied in a very specific field, because they sonify a wave event. Is it possible to generalize the technique by applying it to images to allow even the blind to appreciate the beauty and richness of celestial objects? Indeed, NASA has also led the way in this field and, thanks to efforts to make astronomy more inclusive, a good choice of sonified astronomical images are now available. Much of the work was done or inspired by Wanda Diaz Merced, a blind girl from Puerto Rico who did not want an incurable maculopathy to take away her dream of becoming an astronomer. With great determination Wanda graduated and applied to participate in a NASA internship dedicated to people with disabilities, then earned a PhD in Computer Science from the University of Glasgow in 2013. Proving that she has splendidly overcome the limitations caused by her handicap, Wanda worked in Japan and South Africa. In 2016 she was invited to participate in the Frontiers conferenceat the White House. She collaborated with Harvard University and the International Astronomical Union and has now moved to the Virgo gravitational wave observatory, near Pisa. Here Wanda will try to sonify one of the most elusive and most sensational astronomical phenomena: gravitational waves.
It is a tiny deformation of space-time that originates when two black holes, which orbit one another in a binary system, get closer and closer, until they interpenetrate. The gravitational signal that, in a fraction of a second, increases in intensity while becoming more acute, lends itself to being sonified. It is called chirp and contains information on the starting black holes and on the one that resulted from the merger, slightly smaller than the sum of the two starting objects. The difference turns into a gravitational wave, a phenomenon predicted by Einstein’s general relativity in 1915 and revealed just 100 years later, in September 2015.
A real revolution in astronomy: a chirp of 0.2 seconds was enough to understand that many of the commonly accepted theories on the formation of black holes were to be revised. It is one of the most fascinating discoveries of modern astrophysics which, rightly, gives the title to the beautiful book by Massimiliano Razzano, Listening to the cosmos.. In truth, the book is not limited to gravitational waves, Maximilian describes the new approach that characterizes modern research. To understand the behavior of any celestial object, one must learn to study it at different wavelengths by doing multi-wavelength astronomy, but that’s not enough. We must also be ready to exploit the information that comes to us from the new frontiers of astrophysics from neutrinos to gravitational waves. The new astronomy is multi-messenger. The total picture, which is objectively difficult to compose, is of extraordinary richness. I hope gravitational science will soon become an inclusive art installation
Watch the video on Kepler’s Harmonices Mundi :
Featured image: Harmony of the cosmos. Credits: X-Ray: Nasa / Cxc / Sao; Optical: Nasa / Stsci; Ir: Spitzer Nasa / Jpl-Caltech; Sonification: Nasa / Cxc / Sao / K. Arcand, M. Russo & A. Santaguida
Provided by INAF