Listening to the Universe: A New Way to Explore the Galaxy Simulations with COLIBRE

Team member James Trayford is also a developer COLIBRE simulations, spending a lot of time immersed in detailed, mathematical models while, while trying to keep the ‘big picture’ in mind. With the main COLIBRE simulations now completed, modelling formation and evolution for vast populations of galaxies across billions of years. The volume and complexity of data COLIBRE produces are staggering. With hundreds of physical variables followed simultaneously, building intuition and understanding for what the model can tell us about our Universe is a real challenge.

Traditionally, visual representations have been heavily relied on to understand these models. But through Audio Universe, we have explored a different approach: sonification. By turning COLIBRE data into sound, not only can these complex ideas be communicated more effectively to the public, but it actually helps researcher, gain new insights into the intricate interplay of the physical processes we are studying.

Why Sound? The Limits of Visualizing the Universe

In reality, galaxy formation is a truly multi-scale process. Super-massive black holes accreting matter on scales of light-years, which in turn drive massive, cataclysmic gas outflows that stretch across millions of light-years.

Trying to convey such large and small scale events simultaneously is inherently limited for visuals. Crucial details can get lost because they are smaller than a single pixel on the screen, or rapid variations can happen faster than the frame rate of our videos. With the delicate balance of processes acting in concert to regulate gas inside galaxies, it can be a struggle to visualise the most relevant variables at once.

With the addition of audio, these invisible and micro-scale processes can be represented happening in real-time, while watching the large-scale spatial context of the galaxy evolving on screen. Working directly with this data to build these sonifications using the STRAUSS package can change how we interact with the simulations. It provides a higher-dimensional representation that can reveal the timeline of these galaxies in a richer way, and lends new intuition to the represented data.

Galaxy Physics in Harmony with Sonified Videos

Each of the COLIBRE videos provide spatial maps of physical properties across a field of view. For the sonification, three key rates that work together to drive galaxy evolution were focussed on: the star formation rate, the black hole accretion rate and the energy outflow rate of gas from galaxies. These are 'voiced' by distinct sonification styles in the videos:

• Star Formation Rate (Harmony): A harmonised, musical sonification representz the birth of new stars. The higher the star formation rate, the higher the pitch and intensity of the musical notes. Choosing harp samples, a stack of musical 'fifth' intervals gives us a pleasant sound, well-spaced in pitch.

• Black Hole Accretion (Rhythm): The rate at which matter falls into the galaxy's central 'active galactic nucleus' (AGN), is represented using a rhythmic 'click-train'. This acts a bit like a Geiger radiation counter - a familiar, inorganic sound where a faster click rate means the black hole is feeding more rapidly.

• Galactic Winds (Texture): The energy outflow rate uses a textural sonification. This is mapped to the cutoff frequency of low-pass filtered white noise to create a literal 'wind-intensity' sound. This "skeuomorphic" approach creates an organic 'whooshing' that represents the literal 'winds' carrying gas and energy away.

Introducing COLIBRE's Sonified Interactive Maps

Along with these movies giving new insight into the history of individual COLIBRE galaxies, sound can also help us explore this virtual universe. By combining sonified and visible layers, users can get new insights into hidden physics, such as those ruling the universe we see through telescopes.

By enabling sonification, users can start to uncover physics they don't see simply by moving the cursor, such as the unseen network of matter connecting galaxies in a 'cosmic web'. Can you hear the intensifying whoosh representing higher gas temperatures around galaxies? Or the fast ticking represent the high rate of X-ray radiation? Perhaps the evolving sound of a chord helps you find a clump of dark matter without any stars?

This tool is intended to give users freedom to explore: you can choose to combine and represent layers however you like with our three sonification 'voices', those we developed for the videos. By building their own combination, users can help us to find new and better ways of applying this technique.

The sonified maps are avalaible to explore here.

This interactive tool is just the start - the plan is to develop these approaches and extend them to other areas of science and walks of life through the Audio Universe. 

Learning to listen

Ultimately, sonification isn't just about making cool science communication tools - It's intended to provide richer and more accessible data representation in science. By integrating multimodal tools into major science projects like COLIBRE people can engage with the science in new ways, and sonification ideas can be demonstrates on a big platform.

By ensuring the underlying physical properties are comprehensively represented through sound, we can open up this complex data to more people such as talented students and researchers who happen to be blind or visually impaired (BVI).

Ben Ruggles is the final year of an integrated Masters degree in Physics, Astrophysics and Cosmology at the University of Portsmouth, and is using sound to explore the COLIBRE data from his BVI perspective. Studying the complex link between flows of gas into and out of galaxies, and small scale physics like star formation and AGN accretion, Ben is pioneering new methods at the same time as working towards a better understanding of galaxies. Ben says “I’ve found using STRAUSS to explore complex physics like galaxy evolution a great way to research and develop real scientific questions, whilst demonstrating new efficient and accessible methods for insight into data.”

Discovering things about our Universe often requires looking at the data from new perspectives: perhaps we are starting to listen to what the data tells us.

Find Out More

• Watch & Listen: Explore the full library of sonified movies on the COLIBRE Project Website.

• Get the Code: Want to sonify your own data? The STRAUSS library is open-source and available on GitHub.

• The Science: The COLIBRE website and the growing list of publicly available papers explain COLIBRE in detail - visit to find out more!