Free Astronomy Magazine March-April 2025

28 MARCH-APRIL 2025 by NOIRLab Josie Fenske G alaxy clusters are some of the largest known structures in the known Universe. Current models suggest that these massive structures form as clumps of dark matter and the galaxies that form within them are pulled together by gravity to form groups of dozens of galaxies, which in turn merge to form clusters of hundreds, even thou- sands. One such group is the Antlia Cluster (Abell S636), located around 130 million light-years from Earth in the direction of the constellation Antlia (the Air Pump). This image was taken with the 570- megapixel Department of Energy- fabricated Dark Energy Camera (DECam), mounted on the U.S. Na- tional Science Foundation (NSF) Víc- tor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American Obser- vatory in Chile, a Program of NSF NOIRLab. It captures only a portion The glittering galaxies of the Antlia Cluster T he Antlia Cluster (Abell S636) is a group of at least 230 galaxies located about 130 million light-years away in the direction of the constellation Antlia (the Air Pump). It hosts a rich variety of galaxy types, including lenticu- lar galaxies, irregular galaxies and ultra-com- pact dwarfs. The cluster is dominated by two massive elliptical galaxies — NGC 3268 (center) and NGC 3258 (lower right). [Dark Energy Survey/DOE/FNAL/DECam/CTIO/NOIRLab/ NSF/AURA − Image processing: R. Colombari & M. Zamani (NSF NOIRLab)] of the 230 galaxies that so far have been found to make up the Antlia Cluster, as well as thousands of back- ground galaxies. DECam’s ultra-deep view showcases the variety of galaxy types within and beyond the cluster in incredible detail. Several Pro- grams of NOIRLab (NOAO before 2019) have contributed observations of the Antlia Cluster over the past 20 years. Scientists from Chile have used both the Blanco telescope (with