ID#: 760

From Orion to Cassiopeia (2023) ; 6:27

by Mara Helmuth

University of Cincinnati

From Orion to Cassiopeia emerged from experiments with sonification of pulsar data. One of the more interesting types of celestial objects, these neutron stars emitting electromagnetic radiation are formed when the fire in a star burns up all of the fuel, ending with a supernova explosion. Rotations of pulsars can be so precise as to serve as a clock. Scientists have observed gravitational waves after neutron stars collide. Telescopes on earth detect pulses of many different frequencies and spectra from pulsars across the galaxy. Each pulsar has a unique set of characteristics. Granular synthesis is a logical synthesis technique to use for this sonification because of the appropriateness of mapping the pulsar rotation speed to grain rate and frequency. From Orion to Cassiopeia contains sounds from each known pulsar from galactic longitude 270 degrees to 360/0 to 120 degrees. If you could face the center of the Milky Way Galaxy, the pulsars heard would first be to your right, and moving slowly forward and to the left. A sparse fantasy section in the middle of the piece, from a more stretched out version of the piece, interrupts the high densities near the galactic core. Thicker textures in the piece indicate high density of pulsars, perhaps from the direction of a spiral arm or the center of the galaxy. The lower pitches and rhythms come from mostly older and slower-rotating pulsars, while the higher pitches are from faster pulsars, perhaps those who have spun up after siphoning off material from a binary companion. Data on 3359 pulsars were obtained from the Australian National Telescope Facility’s Pulsar Catalogue and mapped to sound parameters. The rate of grains is mapped to rotation speed as well as grain frequency, and the width of pulse at 50% is mapped to grain duration. The age of the pulsar is translated into duration of the sound event, and more distant pulsars, some as far as 25 kpc away, have sounds with more reverberation. Mean flux density impacts amplitude of a particular sound. Scaling of various parameters was performed with logarithmic, exponential or quadratic functions when necessary. Synthesis was done using new RTcmix granular synthesis instruments programmed by Kieran McAuliffe and Mara Helmuth. The piece was generated from a single script. Bill Gwynne, astrophotographer, sound engineer and musician, created the video from his photos of space.