Below is the optical image of the “Antennae Galaxies” colliding, as taken by the Hubble Space Telescope.
Now, overlaid, is a radio-image taken by ALMA. In the ‘image’ in this case, each pixel is actually represents a spectrum of frequencies across the electromagnetic radio spectrum: the ‘image’ is actually a data-cube.
We have transformed this data-cube in two ways.
Firstly, so you can see it on the overlay, we’ve transformed the radio frequencies into visible, so you can see a slice of the cube.
Secondly, we’ve transformed the e-m spectrum into an acoustic spectrum. Remember light≠sound: what we are doing is translating the frequency of e-m radiation (‘light’) into a frequency of pressure wave (sound).
To view & listen open this link coming soon in a new tab while you are reading this post. That way you wont accidentally hit ‘back’ and have to reload it.
By clicking the image and moving your cursor around you can “play” a spectrum of the colliding galaxies. Underneath, you can see a visual representation of the frequency spectrum. Spend some time moving slowly around the red(redshifted) areas – there is a surprising richness to the harmonics for such a simple sonification.
Note: this loads a 62MB data-cube before displaying (still working on a compressed version) … it could take many minutes to appear if you are on a slow connection – it did take these photons 70 million years to reach us, so please be patient while they go the last few bit-miles!