IC 1101: The 1.7-Million-Light-Year Giant Redefines Galactic Size

Deep imaging of IC 1101 places the edge of its main stellar body at about 260 kiloparsecs from the center, corresponding to a diameter of roughly 1.7 million light-years—the largest galaxy known. Although its core ends, faint outer structures indicate ongoing accretion, likely from past mergers, with X-ray gas disturbances suggesting a merger history. Located in the Abell 2029 cluster, IC 1101 may still grow and could be one example of a population of ultra-giant galaxies awaiting discovery. The study, accepted in Astronomy & Astrophysics, demonstrates how pushing imaging depth reveals the outskirts where galaxies continue assembling material.