Quirks & Quarks

An astronomer turns the motions of our Milky Way galaxy into sweet music

Decades of radio-telescope observations are converted into a three minute jazz tune.
Decades of radio-telescope observations of our Milky Way galaxy are converted into a three minute jazz tune. (The Associated Press)

"Music of the spheres"

In medieval times, people would speak of the "music of the spheres", imagining the motions of the stars and planets as reflecting a kind of music. An American astronomer has taken this notion one step further by taking decades of radio-telescope observations of our galaxy to use as the source and inspiration for a musical composition he's calling the "Milky Way Blues."

Radio telescopes all over our planet monitor the skies for radio waves given off by clusters of stars, clouds of interstellar gas and other phenomenon in the our Milky Way galaxy. These observations give astronomers important information about parts of the galaxy we can't see with the naked eye. But astronomer Mark Heyer from the University of Massachusetts in Amherst thought he could make even more of these observations, and made a piece of music that encapsulates the 20 years' worth of data.

Turning astronomical data into music

Heyer got the idea for the musical composition 25 years ago when his university's telescope was making immense, three-dimensional images of radio emissions from molecular gases in the Milky Way. But as someone with a keen interest in music, he started wondering if all this wealth of information could be represented in sound as well.

He thought perhaps pitch could be used to represent gas moving in the Milky Way.  A rising pitch could represent gas moving towards us, a falling one, gas moving away. That way, you could "hear" the direction of gases moving in the galaxy. With that as a start, Heyer said, "I thought we could do even something more interesting — we could make music out of that."

At the time, he would have needed an expensive orchestra to turn the astronomical data into music, so the idea lay dormant for many years. But recently, Heyer's brother made him aware of modern software that lets you input a set of notes that can then be played back with the sound of any instrument.

An all-sky view of our Milky Way Galaxy and neighbouring galaxies based on measurements of nearly 1.7 billion stars observed by the European Space Agency's spacecraft Gaia. (ESA via Associated Press)

That inspired Heyer to revive his idea and his musical science really took off. He wrote his own software that transposed the inherently atonal astronomical data into musical notes. He then fed that into the playback software selecting different instruments for different astronomical phenomenon. In the end, he was able to hear the data as the galactic ballad it was.

The sounds of the Milky Way's gas

Gases in the Milky Way generally rotate around our galaxy's centre, and they come in various types: molecular, ionized and atomic. When listening to Dr. Heyer's soundscape, one can pick out the molecular gases, which are played by the wood bass and piano; the ionized gas heard as the saxophone; and the atomic gas which is represented by the acoustic bass.

Where you hear a lower-pitched instrument, that means that the gas is moving away from us. When the pitch is higher, that indicates the gas is coming towards us. As a result, when you listen to his music, you are listening to an accurate representation of the rotation of the galaxy.

Artist's impression of a black hole, like the one at the centre of our galaxy (NASA)

The final piece of music is all based on real data. Dr. Heyer attests that there has been no tinkering or massaging of the sounds to make them sound more palatable to the human ear.

And if you listen closely, you can even pick out certain identifiable features in the Milky Way, such as the supermassive black hole that sits at the very centre of our galaxy. It is roughly four million times more massive than the sun, and as a result, all gases near it get distorted.

Listening to the cosmos

Although gases still rotate around this black hole, their rotation is moving much faster than in other parts of the galaxy that they've sampled. The increased speed and distortion can be heard clearly in a quick run of fluctuating notes.

It took Dr. Heyer months to assemble the data into music, so it's much tougher than just sitting down at the piano to play a little riff. The result may not be the kind of music you're used to, but it is a powerful contribution to the sonification of scientific data.