Astronomers may have discovered how galaxies change their shape

Astronomers may have discovered how galaxies change their shape

Researchers may have answered a decades-old question about galaxy evolution, leveraging the power of artificial intelligence (AI) to accelerate their research.

Ever since the Hubble Sequence, that classifies galaxy morphologies, was invented in 1926, astronomers have been refining our understanding of evolution and morphology as our technology advances.

By the 1970s, astronomers had confirmed that lone galaxies tend to be spiral-shaped, and those found in clusters were likely to be smooth and featureless, known as elliptical and lenticular (shaped like a lens).

The new research led by astronomers at the International Centre for Radio Astronomy Research (ICRAR) may have uncovered the reason for these differences in shapes.

See also: Australia’s WALLABY adds to knowledge of nearby galaxies


Lead author Dr Joel Pfeffer from the University of Western Australia node of ICRAR, said the research explains the ‘morphology-density relation’ – where clusters appear smoother and more featureless than their solo counterparts.

Pfeffer said: “We’ve discovered there are a few different things going on when we get lots of galaxies packed together. The spiral arms on galaxies are so fragile, and as you go to higher densities in the clusters, spiral galaxies start to lose their gas.

“This loss of gas causes them to ‘drop’ their spiral arms, transforming into a lenticular shape. Another cause is galaxy mergers, which can see two or more spiral galaxies crashing together to form one large elliptical galaxy in the aftermath.”

The study utilised the powerful EAGLE simulations to analyse a group of galaxies in detail, using an AI algorithm to classify them by their shape.

The neural network-based algorithm was trained by ICRAR PhD candidate Mitchell Cavanagh and can classify almost 20,000 galaxies per minute, compressing what would typically take weeks into one hour.

The simulations closely match what has been observed in the universe, giving astronomers the confidence to use the simulation results to interpret observations of clusters. 

The study also identified several lenticular galaxies outside of the high-density regions where they are expected, with the modelling suggesting they were created by the merging of two galaxies.

Pfeffer said the work brings together various pieces of research in galactic evolution, to understand the morphology-density relation for the first time.

“There’s been lots of suggestions over time,” he said. “But this is the first work to really put all of pieces of the puzzle together.”

The research is published in Monthly Notices of the Royal Astronomical Society.

Image: A representation of how the EAGLES programme classifies as assessed by AI. © ICRAR.

Leave a reply

Your email address will not be published. Required fields are marked *

Aether: Issue 3 Feb 2023

Aether: Issue 2 Nov 2022

Aether: Issue 1 Aug 2022

Subscribe for free

Latest Testimonial

What a beautiful motto: Discoveries must be read and not just published. When I was contacted by Aether as a new digital service to share scientific and technological insights I had my doubts that this was really going to be according to what I call the “open source & makers’ spirit”: knowledge should be free and it is there to be shared.

Well, Aether is faithful to its motto and shares discoveries freely. It has been a pleasure to collaborate for the interview and subsequent article. It has been greatly self satisfying to see how the interview was professionally and truthfully redacted and then published. Sharing thoughts and sparks for discussions is fundamental to the progress of society. Your journal offers clarity and brevity and I believe it provides the sparks to ignite any reader whether academic or not into action.

Dr Maria-Cristina Ciocci
Co-founder and Manager of non-profit organisation De Creative STEM,GirlsInSTEM