GGCs database: The Sound of Clusters

Release 11.12 ("Hergest Ridge")

The Sound of Clusters (v. 0.1)

i.e., how to realize great (?) contemporary music with a little help from good old globular clusters...

In this experiment, we tried to find a way to obtain a sort of sound for each globular cluster. For the generation of sound files we used the IDL package, that it is able to create WAV files with given values.

To obtain a sort of STEREO effect, we worked separately on two channels (left and right).

The procedure adopted run as following. We crossed each cluster along the X coordinate, which also interesecate the center of the cluster. This X cordinate is put in relation with time, since the cluster is crossed at a constant rate.

Note that, in the presented realization, only the most luminous 3000 stars are taken into account.

In crossing a given cluster, each star generates a sound (detailed as follow), different for each channel. Sound belonging to each stars is then summed to compose a complex pattern, which is the one you can hear clicking on the button.

Here is the sound of NGC 104 (You can access other file sounds, when available, from the pages of individual clusters or via this page)

Here is a video animation for what concerns NGC 6934


- Each sphere rapresents a cluster star, where...
- POSITION is computed according to the catalogues (see below)
- DIMENSION is proportional to absolute magnitude (largest stars are the most luminous)
- COLOUR is related to the effective temperature (via a specific colour table)


- TIMBRE is given by a series of overlapped cosines  
- FREQUENCY is a parameter who depends from (V-I)_vega
- INTENSITY is a combination of V MAGNITUDE and Y COORDINATE 
- DURATION is a function of MAGNITUDE


- TIMBRE is a simpe cosine 
- FREQUENCY is a parameter depending on (V-I)_ground. (Note that it is almost equal to the frequency of first channel, but not completely equal - in order to allow beats)
- INTENSITY is a function of I MAGNITUDE and Y COORDINATE (distance)
- DURATION is a function of MAGNITUDE

To generate these sounds we have used the data included in the serie of works by Sarajedini et al, The ACS Survey of Galactic Globular Clusters.

In passing, one may be interested by the simple evidence that this automatic procedure seems to generate sound patterns which are (broadly speaking) not too distant from real contemporary music...

Ivan Ferraro, original concept and realization
Marco Castellani, collaboration, adaptation for Internet

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