A swirling galaxy

eso_potw2640a October 5th, 2026

Credit: ALMA(ESO/NAOJ/NRAO)/J. Koda et al.

Like a portal to another dimension, a hypnotising swirl features in today’s Picture of the Week. This is the spiral galaxy M83, also known as the Southern Pinwheel, located approximately 15 million light-years away. It is one of the brightest galaxies in the night sky, but this image –– taken with the Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner –– doesn’t show how M83 looks in the light our eyes can see. Instead, it depicts the light emitted by cold gas molecules, the ingredients of star formation. Astronomers are interested in molecular gas clouds as virtually all stars are born from their collapse. Once stars form, they heat up their surroundings, making it harder for gas to condense and form further stars. This, combined with galactic dynamics that continually stirs gas, controls the growth of galaxies. ALMA allows astronomers to map how the density and temperature of these gas clouds change in different locations within a galaxy, such as the central regions, the spiral arms, or the space between them. This in turn helps us understand whether stars form differently in different galactic environments. M83 closely resembles our own galaxy, the Milky Way. Since M83 appears nearly face-on in the sky, astronomers enjoy a privileged view to study whether the recipe to turn gas into stars is universal or changes within M83. Links M83 in visible light Interactive comparison of M83 in visible and submillimetre wavelengths Research paper in The Astrophysical Journal by J. Koda et al.

Provider: European Southern Observatory

Image Source: https://www.eso.org/public/images/potw2640a/

Curator: European Southern Observatory, Garching bei München, None, Germany

Image Use Policy: Creative Commons Attribution 4.0 International License