Displayed above are eight galaxies imaged by the Sloan Digital Sky Survey. Although all of these galaxies are spiral galaxies, there are large differences between them: the top row shows grand-design spirals, which feature well-defined arms, and the bottom row shows flocculent spirals, which have feathery or patchy arms. Recently, a team led by Biju Saha (Indian Institute of Science, Education and Research) explored whether grand-design and flocculent spirals could be classified by their fractal dimension. With intricate structures on scales large and small, spiral galaxies are fractal-like, and fractal dimension is a way of quantifying the complexity of their structure. Saha and collaborators found a statistically significant difference in the median fractal dimension of their samples of grand-design and flocculent spirals, suggesting that this mathematical method can help distinguish between the two types of spirals. To learn more about how fractal dimension is calculated from galaxy images, and what these results might mean for how spiral arms form, be sure to check out the full research article linked below.
Citation
“Can Fractal Dimension Distinguish Between Grand-Design and Flocculent Spiral Arms?” Biju Saha et al 2025 ApJ 991 63. doi:10.3847/1538-4357/adf840