Euclid Telescope Survey Analyzes 380,000 Galaxies to Probe Spiral Arm Origins

A new study led by Smith et al. (2026) used observations from the Euclid space telescope to assemble a sample of more than 380,000 galaxies, the largest dataset of its kind for galactic morphology. The researchers measured each galaxy’s number of spiral arms together with stellar mass, star‑density concentration and star‑formation rate, seeking statistical patterns that could explain why spiral arms form and persist.

The analysis shows that roughly 60‑70 % of spiral galaxies possess two prominent arms, and it identifies correlations between a galaxy’s mass and the likelihood of having multiple arms. The study also reiterates that spiral arms are not solid structures rotating with the galaxy; instead, they arise from differential rotation, where inner disk regions orbit faster than outer ones, preventing rigid arms from surviving many rotations.