Free Astronomy Magazine March-April 2025

MARCH-APRIL 2025 T his excerpt shows a small selection of the myriad picturesque galaxies that can be found within the Antlia Cluster — a group of at least 230 galaxies located about 130 million light-years away. This image was taken with the 570-megapixel Department of Energy-fabricated Dark Energy Camera (DECam), mounted on the U.S. National Science Foundation (NSF) Víctor M. Blanco 4- meter Telescope at Cerro Tololo Inter-American Observatory in Chile, a Pro- gram of NSF NOIRLab. It captures only a portion of the 230 galaxies that so far have been found to make up the Antlia Cluster. DECam’s ultra-deep view showcases the variety of galaxies within and beyond the cluster in incredible detail. [Dark Energy Survey/DOE/FNAL/DECam/CTIO/NOIRLab/NSF/AURA. Image processing: R. Colombari & M. Zamani (NSF NOIRLab)] The cluster is rich in lenticular galax- ies — a type of disk galaxy that has little interstellar matter and thus lit- tle ongoing star formation — and also hosts some irregular galaxies. A plethora of rarer, low-luminosity dwarf galaxies have been found in the cluster, including ultra-compact dwarfs, compact ellipticals, and blue compact dwarfs. The cluster may also contain dwarf spheroidal galaxies and the ultra-diffuse galaxy sub- type, though further investigations are needed to confirm them. Many of these galaxy types have only been identified within the past few decades because of advances in observational equipment and data analysis techniques that can better capture the low luminosity and rela- tively smaller size of these galaxies. Evaluating galaxy types allows as- tronomers to plot the fine details of galaxy evolution, and some galaxies rich with dark matter provide further opportunities for astronomers to un- derstand this mysterious substance that makes up 25% of the Universe. The development of larger and more highly sensitized cameras like DECam