Free Astronomy Magazine November-December 2023

25 NOVEMBER-DECEMBER 2023 ASTRO PUBLISHING from the smaller galaxy’s disk. Those stars began to gradually mix with the larger galaxy’s outer halo, forming concentric bands, or shells. A simple anal- ogy is adding a drop of food color to a bowl of bat- ter that you’re slowly stirring. The drop gets stretched out in a spiral that remains visible for a long time before completely mixing. The shells of NGC 3923 make the galaxy quite excep- tional. Not only does it have the largest known shell of all observed shell galaxies, but it also has the E xcerpts of the galaxy-rich image showcasing NGC 3923 taken by the US Department of Energy’s (DOE) Dark Energy Camera mounted on the National Science Foundation’s (NSF) Víctor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American Observatory in Chile, a Program of NSF’s NOIRLab. [DESI Legacy Im- aging Surveys/LBNL/DOE & KPNO/CTIO/NOIRLab/NSF/ AURA. Image processing: T.A. Rector (University of Alaska Anchorage/NSF’s NOIRLab), M. Zamani, R. Colom- bari & D. de Martin (NSF’s NOIRLab)]